LUVN'NOS

i have a 91 LB9 trans am that hasn't ran good in a long time. It was my moms car and i really want to get it driveable. It used to just have a choppy idle and the CEL would pop up and i had a code 33...i replaced the MAP sensor and nothing, but sometimes it would run completely fine with no problems at all, sometimes it would just have a lope in the idle, sounded like it had a hot cam sorta, but no hesitation on acceleration and ran great when you were moving, but sometimes it wouldn't idle at all and would shake and shudder throughout the RPM range. It confuses me because it would run fine for awhile, than maybe i would shut it off, start it, and the CEL is on and idle is loping, and than shut it off and it wouldn't idle at all. But now i can't get it to idle at all and when i rev the engine a bit it shakes and shudders in neutral, and i can small lots exhaust, possibly even a gas smell in the exhaust. My dad said it might need a new distributor cap, rotor, spark plugs and wires, but i don't know, can you guys please give some things to check because i have no idea where to start. thanks in advance

Supervisor42

If the tune-up stuff hasn't been done in years, might as well go ahead and do it. It's not too expensive and not that difficult (except for the usual pain with the sparkplugs).
I sounds like it may be the EGR valve sticking, which is a big pain to change...

LUVN'NOS

ok thanks, will try that in the morning and i'll check the egr valve. I was also told it could possibly be a vacuum leak or a bad ground or something at the MAP sensor, any chance of that and how to check for it?