Hello everyone! I have a 97 S14A with a black top SR and I recently installed yellow 550cc nismo injectors, and the car runs fine on idle and cruising and when flooring it, it runs good until about 4500 rpm and the car stutters really hard like it is leaning out or not getting fuel but according to the afr it is not leaning out at all, a little rich around 11. I also have Greddy Emanage Ultimate so i went and changed the after injectors to 550 and also played with the injectors to make the afrs somewhat good. I also have a walbro 255lph fuel pump. Anyone got any suggestions to what might be causing this? All help is appreciated