 Strange Stuttering and low idle
Hi, im new to here and i stupid when it comes time to work on cars. i have a 98ZX2 5 spd for about a year now. since i've gotten it its done this weird stutter when i accel and drop to 500 RPMs at lights. it doesnt do it all the time, VERY VERY random times. i have a cold air intake since ive gotten it. recently put on a pacesetter header and pipes, left cat there. i'm told to knock it out to make it louder but debating on that. but iv'e fixed everything i'm told could be the problem but still does it. what it does is in ANY gear i'm in if i slightly press accel it will stutter along for a bit then kick in and go. and if i'm at a light or sign the RPMs will drop to around 500 and try to die off. i still have the check engine light on but i'm told its due to O2 sensor. so i wanted to ask if anyone would know how to make it stop, if that is the problem or something else. the O2 sensor has only been reading since i put on header and pipes so thats why u question it. otherwise i'm out of ideas, thanks for your help | 
