I drove to work tonight and my car seemed to be fine. After work I started it up to leave and it won't run. It starts just fine, then the idle drops low like around 500 rpms, and it fluctuates a little. When I feather the gas pedal it hesitates and revs up as I let off the gas. If I floor it it will either die, or hesitate and then rev up but it's really rough, like it's missing on a couple cylinders. Any ideas? Thanks for any help.

P.S.-The car is a 1988 IROC-Z 350 TPI. Only mods are catback and k&n's.

 

Check fuel pressure when the problem is occurring.

 

It was the maf, just in case anyone runs into a similar problem.