I took off my smog pump on my 91 rs 305tbi camaro and put on new headers and exhaust today and i had to run a longer belt.... but now since all that is off my car is ideling rough and when driving up a hill or acceleration, it will cut in and out from 1500 to 2000 etc at diferent RPMS and my service engine light is on. could that be my O2 sensor thats bad? and is there a different type of O2 sensor i shoud be using since i have headers? But could the car need a tune up now since i hat to run a longer belt?

Thanks, Nelson. i could really use some help on this