I've got an 82' Z28 with crossfire, you might want to check the sensor that is located on the left hand front of the intake manifold, just to the bottom left of the thermostat housing. It has (2) wires attached to it, one black, one yellow. I'm not for sure what it's called, but it regulates the amount of gas that gets sprayed into the throttle bodies, depending on the operating temperature of the car. I know if this wire gets disconnected, which it did on mine by accident, that it will flood the engine, and it will be hard to start, and it will run like crap. You also might have clogged filters, they are easy to clean out. Each side has (1), just follow your gas line until you find it, its connected to a big 1 inch nut.
All you do is loosen the nut, I had to use a large crescent wrench, take it out, it will probably be black like mine were, there's a spring attached to the end of it. I soaked mine in carb cleaner for an hour or so, and put them back in, it ran 100% better, I was having problems with it surging at idle........Good luck. KZ