1994 Z28 is running like crap. Step on the gas and it misses like crazy and I hear a pinging sound which I think is pre-ignition. Even misses badly while idling. Only happens as far warms up. No problem when it is cold. Any ideas?

 

9/10 its the opti. Always gets worse when it gets warmed up.
If it's not opti, though, it could be a number of different things, such as sensors, dirty injectors, etc. But if it's knocking it means its a problem with your ignition...