Lately I've noticed my car misses at idle and seems to stumble right after I make a shift (approx.2000rpm) but then runs fine from about 2500rpm on up. My gas mileage has been off a little bit. I usually average 24mpg but lately have been getting around the 21mpg range. My spark plugs and wires have 5,000 miles on them. Today it blew black smoke at the top of 3rd gear while I was racing an IROC. The car has 110,000 miles on it, and I know the opti will probably go sooner than later, but is there anything else it could be? It has never been tuned, but has had the EGR, AIR, and Catalytic converter removed, as well as longtube headers, LT-4 Knock module, and descreened MAF. Should I get it tuned or should the stock tune be fine? Could that be causing my problems?

Thanks
Clint

 

Any ideas? I'm leaning towards the opti, but I wanna cover every angle to be sure.

 

Sounds like the opti to me. The car will certainly benefit from tuning, but you have to take care of the other issues first.