I cam onto this info thought I would share because I was a unsure about the subject here goes -

Because of the large amount of questions I receive about the O2 sensors and all of the incorrect information we have seen on the 07-08 Harley EFI, I will further explain how the closed loop EFI system works on the Harley Delphi system and why Dynojet has developed the Power Commander with O2 sensor eliminators. First I will start by explaining how the narrowband O2 sensor works. Keep in mind the O2 sensor is only one of the many sensors which monitor engine functions in the EFI system. The narrowband O2 sensor can only accurately measure a small area within 14.7:1 stoichiometric air/fuel ratio range and works by providing a voltage signal to the ECM which then will continuously monitor the stoichiometric mid point crossover and adjust accordingly until the A/F is in the 14.7:1 range. The ECM is only using the O2 sensor feedback signal when the system is in closed loop mode. Closed loop mode occurs only under certain conditions which are light load, steady speed part throttle, constant mode. It is only after these conditions that the will EFI go into closed loop mode and the ECM will adjust until the O2 crossover point is in the 14.7:1 A/F range. Simply put, an narrowband O2 sensor only works for adjusting low load/cruise area and does not work well in performance applications because it can only monitor a small area within the stoichiometric A/F range. With that being said, yes the stock EFI can adjust itself on the 07 Harley models. That is if you consider the small amount of time it is in closed loop, and then when the ECM is able to adjust A/F it can only adjust it within the 14.7:1 range which is WAY too lean. For reasonable performance and drivability this 14.7:1 A/F is extremely lean and this is the reason for the 07 bikes to run very hot with poor drivability. This condition gets even worse when you change your exhaust or air cleaner. Optimum A/F ratio for cruise area is 13.4-13.6:1 and 12.8-13.2:1 for wide open throttle. When you install an aftermarket EFI module (regardless of manufacturer) you will need to eliminate the O2 sensors with eliminators that send a fixed signal. This will prevent the EFI from going into closed loop mode and you will be able to tune to an optimum A/F ratio for the bike to run properly, otherwise the stock O2 sensors and closed loop mode will try to lean the mixture within the 14.7:1 range. Even with the Harley Screamin Eagle Race Tuner in which you can retain the O2 sensors, again you can still only work within the stoichiometric range which the only voltage the O2 sensors can measure. Dynojet certainly has the technology to develop a Power Commander for the Harley models with a Wideband sensor that replaces the stock O2 sensor which would be able to tune in real time to target A/F ratios, Power modes etc.. although with the relatively simple design of the Harley/Delphi injection the current Power Commander USB is more than capable of adjusting what we need to adjust at the moment. Keep in mind in Japanese applications the Power Commander is widely used as well in EFI systems that are far more complex with technology such as Dual ECU's, computer controlled secondary throttle blades, multiple staged injectors for each cylinder, fly by wire throttle and for 2007 computer variable intake length. From our experience tuning bikes everyday we know the Power Commander is the best EFI module available and works like no other to effectively adjust the EFI in the full range of RPM's and throttle positions, including the light load/steady cruise areas. Keep in mind that our maps are developed using different modes for light load/cruise area and for upper RPM full throttle performance. We have seen excellent results on the 2007 bikes and will increase your riding enjoyment. I hope this has helped with any questions.

SOURCE 1130CC V-ROD WEB SITE  The info comes from the chap from motofuel. In the US.