I have a 87 Z28, 305, 5 speed. The car has set up for about a year. I installed a new stock replacement clutch and new plugs. The gas tank had been full when I started it. I ran the tank to about a quarter and then refilled with premium gas and some sea-foam. The problem is that once the clutch is released, the motor/car bogs down like it it under an extreme amount of load. Once the rpms are brought up above 3k to 3500 does it seem to come alive and want to run. Also the car runs with an almost miss at low rpms. If anyone knows of anything I can check or give me a place to start looking, I would appreiciate it.

 

Check your EGR valve, sounds like it isn't working correctly, either it's plugged or has gone bad.

 

possibly a clogged cat as well?