i have a 91 formula 305 tpi its stock besides a flowmaster muffler its running rich all 8 plugs are black when you mash the gas it a black cloud behind you.
it has 256,000 miles on it dont look like its ever been apart i did clean the throttle body and Iac. i was going to put o2 sensors on it but havent yet the check engine light comes on everyonce in a while tried to flash a code out but did not get one dont have a scan tool yet. i was wondering if you could give me any ideas were i might start looking. thanks

 

well, there are a few possibilities. it could be the o2, could be the fuel pressure reg, could be dirty intake (carbon deposits). do you have a hayes/chilton manual? if so you could take a paper clip and touch the last two terminals on the right? (not sure, anyone verify this?) , upper and lower causing kind of a bridge and that will flash your codes. look in repair manual to find out what codes mean.