The thunderslides I have seen are black plastic so you can see the difference as the OEM's are aluminium. The thunderslide gets mixed reviews so research first before you spend $$$. I wouldn't have one myself.

For good info on tuning a stock CV carb google the nightrider site and find the performance section for carb tuning. There is a lot of good info on tuning the HD CV carb.

I had one years ago & thought it improved the response over the stock cv  pretty well.

Then I put on an S&S & didn't really notice any difference.

try this...         http://www.nightrider.com/biketech/hd_cv_mods.htm