the stock ecu doesn't see the fuel pressure as it is a fixed setting. so the fuel maps will tell it to open the injectors for the same amount of time and you will run lean. the fpr itself won't give better performance, it is a support part, that is it enables you to run mods that will make more performance.

the ait sensor will cause the ecu to lean or richen the mix, but not enough to make it worth the time to mod it.