As I guess you know high flow exhausts like your Short Shots allow more fresh air to be pulled into the pipe, causing the exhaust temperature to rise and detonate any unburnt fuel.

By inserting a screwdriver in each flute you can enlarge the opening which further interrupts the exhaust flow, problem is to get any noticeable change that will reduce the popping you need to cut the flutes and dramatically push them into the gas flow.   Ultimately this fails as it makes the exhaust sound horibbly chuffy. I also extended the V&H baffle but it too failed.

Yeah your EFI runs variable parameters but has limits, exceeded by installing an open exhaust.

The stoichiometric mixture for a gasoline engine is the ideal ratio of air to fuel that burns all fuel with no excess air. For gasoline fuel, the stoichiometric air–fuel mixture is about 14.7:1 i.e. for every one gram of fuel, 14.7 grams of air are required.

When you put your freer flowing intake and exhaust you cause the bike to run lean, and this causes "popping on decel" 

Earlier bikes had a ECM with no oxygen sensors , and later ones have "narrow band sensors" meaning the range of adjustment is small or non existent.

The cure is a new map in both cases , or an aftermarket tuner ( such as thundermax with auto tune) which supply maps for different engine configurations, and has wide band sensors allowing the bike to readjust to stioc and thus reduce or eliminate the decel popping.

I have a thundermax for sale???

The reality as indicated by Dicko is to get a proper tune. The Thundermax system is great but not cheap and you’ll need to learn how to operate it, not terribly difficult and it works. Then you can change the intake or exhaust as you like and retune it yourself.

Short shots are a worse pipe again. Too short, too open and obnoxiously loud. Factory headers with a decent pair of mufflers will run better. Even totally stock pipes may perform better. 

Your bike’s gonna run lean too and that’s what the popping is. Baffling may richen it up slightly but it’s still likely to run lean until the tune is adjusted properly. Running an already hot air cooled engine lean isn’t good. I’d be inclined to spend extra dollars to have it tuned properly given the value of our bikes. Bike will run a lot better too. 

Hundreds of Dollars

You have a Powervision License Key, that allows SHOP to put a tune on your bike. That Key should be transferable so you can go to another shop if have too. 

Give shop feedback and see if they can change the Tune a bit. 

Often the decel pop is more noticeable with non-stock pipes.

Well yeah fuel economy will go down because the simplest way to stop the pop is add fuel.

Here's what one tuner reckons on the net

"For Delphi fuel injected bikes, we have found that adding fuel is needed to reduce popping."

So yeah, adding fuel to a point in the map where it would normally be zero, on decel (and where it's of no use in powering the bike) is simply wasted fuel but it's an easy fix.

Also you've fitted what are essentially drag pipes, not sure if you changed air intake, but one way to look at an engine is like a vacuum cleaner, the better it performs the harder it sucks and engines suck air and fuel. 

I wouldn't blame the previous tuner, it might be subject to what you asked for.  If you just asked them to stop the pop, they've done the right thing at least cost to you.  If you specified that you wanted to stop the pop and maintain economy and lower end throttle response, most likely they would have considered the whole induction/exhaust/timing system and run a full Dyno and that's more $$$$ from you.

So yeah, as someone me, with far less experience I agree with Grease Monkey but also note that having had my bike tuned with a heavy breather and V&H exhaust 2 into 1, I'm still getting around 15kpl, but jeeze she goes.

The TTS tuning module is as good a manual as you’ll find on tuning the Delphi harley ecu. Here’s what it says about exhaust popping. 

***************************************

“Exhaust Popping on Deceleration:

Exhaust popping on deceleration is due to a too lean or too rich mixture in the exhaust. This can be caused by a leaky gasket, or by the AFR being set incorrectly by the ECM. Most commonly, the mixture will be too lean. The ECM has three tables which affect this: Decel Enleanment, the AFR table, and the VE table.

The Decel Enleanment only acts for a short time (ie 1-2 seconds) after the throttle is closed. To richen the mixture during this time, decrease the value in the table at the temperature the problem occurs.

To richen or enlean the mixture during the entire decel event, change the AFR table in the in the first column (20 kPa between 1750 and 3500 RPM by 5 to 10 percent. Some experimentation here will find the sweet spot that eliminates the popping.

In the past, others recommended to change the VE table values to eliminate this popping. This will also work, however since changing the VE table has many other effects on engine operation, we do not recommended it.

Tip: To determine the MAP and RPM that is causing the popping, use the following procedure to "mark" the data recording.

Set-up DataMaster to record generic or O2 data

When you are riding and the popping occurs, pull in the clutch and let the engine revs drop to idle

When you play back the data, look for the idle spot at speed. The MAP and RPM that caused the popping are right before this.

Another way to mark a recording is to pull the clutch in and rev the motor twice quickly. Find a method that works best for your situation!”

***************************************

And to clarify popping that comes in small multiples is a lean issue. One large pop/bang after a releasing a big handfull of throttle is a rich issue. 

You only usually have to fine tune and adjust a very small amount of cells to address the problem if the fix isn’t resolved by the decel enleanment table on its own. 

Reading plugs isn’t always helpful with fuel injection as you can be rich in some parts of your tune and lean in others. How are the plugs gonna show that unless it’s rich or lean all over the tune?

“Dicko , it’s an earlier non oxygen sensor 2006 TC , oldie but a goody . It’s had a power vision dongle tune twice but not fixed the problem”. 

Who did this? If it was paid work, take it back to them. A competent tuner should be able to easily resolve this. Even if not a dyno operator, they should still be able to easily resolve this if they have any idea of what they’re doing. If they don’t or won’t, they shouldn’t be charging money for what they’re doing 

Even flash tunes provided over the internet from overseas (places like fuel moto who sell and support power vision, and Vance and Hines for their Fuel Pak) provide updated tunes to their customers to fix issues like this. 

I listened to the Kevin Baxter video with interest; it was like going back twenty five years!   His observations are on the money, a plug can tell you a lot and his explanations are very comprehensive. Also his comment about race engine plug reading is true, although for a long time now data is king, what the data tells you about a tune will outweigh a plugs reading for adjustments... But,,  that is him and a very few other people I would say, the average punter could observe a lot of what he has talked about , but would they be able to convert observations into corrective adjustments?

 Over the years I have seen bikes of the carb and trigger plate ignition type tuned to a standstill by guys that have had plugs in and out that many times the plug should have wing nut paddles on it, I have seen ignition plates with screw clamp marks across the full range of the slots, and as an example, carburetors with the most bizarre jets installed, a dead giveaway for this is when someone rings asking for something like a .026 inter and 84 main for a S&S E carb, these carbs for one are pretty linear in their inter and main requirements,  if someone asked me for that combo of jets and the outcome was effective, it would tell me the float is way too high [smaller than normal inter]and the fuel supply is restricted [larger than normal main].

When guys say they have the timing spot on to the manufacturers setting, this tells me the engine has probably got the wrong timing as far as optimal is concerned. The factory setting will work perfectly in Anchorage Alaska in winter and Alice Springs Australia in summer, it is fail-safe. Optimal ignition is whatever the engine wants under full temp and grade of fuel conditions, variable load/MAP conditions will also dictate whatever they ask for.

A point not raised in the video is that the porcelain of the plug is self-cleaning at 400°c that is why plug heat ranges vary over some engine models, a colder plug does not necessarily mean a higher performance engine it just means the colder plug will take less heat soak [shorter conductance path] to get to 400°c, conversely a hotter plug heat soaks slower [longer conductance path] and will take longer to get to its operating temperature.

All conjecture aside, I would have to say the technology available today far exceeds any human observations/efforts in our area of interest. Optimal timing across the full rpm range is whatever degrees produces the peak amount of torque for a given rpm and conditions, fuel will also be whatever a particular engine asks for. Over the years we have seen guys swap their magic map into another bike and the results have not been the same, it may work sometimes,,, may,,, that does not make you a gun tuner, just lucky.

For me? I’ll stick with my [old] mate.

At the end of the day, it’s your bike, do whatever you want with it!

Cheers.