i am pretty sure this started a while back.. when i had my bassani x pipe replaced with another bassani x pipe. some time after i replaced the x pipe (2 cats) it threw a code saying front left o2 sensor was running slow. i then replaced my mil eliminators on the rear o2 sensors, and replaced the front two 02's. the code came back on aprox. 20 miles later. i then took the car to the shop. the guy did some diagnostics or w.e and said the code was the same. slow front left o2 sensor. he replaced the 02 sensor and the car drove fine for 20 miles and the light hten came back on. i ended up taking the car back and he replaced that o2 one more time... same story, the light came back on about 20 miles later. the car however runs poorly... it doesnt really pull below 3,000 rpm, it idles roughly and i am pretty sure it started doing this recently and its getting worse; when driving in lower rpms around 2k, it kinda jerks slightly back and forth.. if i give it gas it stops doing it. it never did this before and its really getting obvious and noticable now. another thing i did, was i recently put in a fuel system cleaner. this actually made the light go off and the car drive fine for 95 miles or so. its still idled a little rough but drove much smoother. i now believe the problem is somewhat fuel system related; perhaps my injectors etc. is their a way for me to test them out to see if i have a bad one? anyone have any experiences with similar situations? i am also wondering what will happen if i replace all of my injectors with larger ones since i am planning to get a blower in the future.. is it ok to run that way for several months? what other things could it be? thanks alot i know this isnt the shortest thread.... but i had this problem for a while now and its really getting old. thanks alot for the help.