help PLEASE!!!

[JPE240]

I have a 91 le hatch that will start up, idle high then miss fire as its reved, also if the car is left running the rpms go up n down, crapy idle, and eventually jerk back n forth real hard and shut off.it has headers n exhaustwhat could it be? the car will miss going up to 3000rpms then backfire repeatedly and not go any higher in revs. also when i shut the car off the engine turns over a couple of times after the key is turned, and stumbles to a stop....

timmimg?distributor?the car has new plugs, fresh battery,plentty of gas,

[MaximA32]

Have you checked your IACV to make sure it's operating properly? how -to sticky at the top of this forum for specific directions on how to clean it. Let me know of your progress.

[PantherRacer]

You might have a vacuum problem. check your hoses for leaks to make sure there isn't any un-metered air getting in or metered air getting out.