Rough idle 1989 Corvette Coupe TPI 350 cu. in. has rough idle, misses at cruising speed.

The dist. is a half tooth off location. Pull the dist. an reset timing. Be sure #1 cyl. is at the top and the rotor is pointing to #1 in the cap. or firing order.

EGR sticking or mixture control solenoid on carburator if equipped

clean throttle body with carb cleaner

You need to check for fault codes, the check engine light is on because a fault is in the system. Here is how to do a fault code test, no special tools required. Follow the link please. FAQ How to read older GM codes for free

check the fuel injectors - seems the new fuel is messing these up...

i want to give you the right answer but the only thing i think of is the mass air flow sensor.

The 5.0L injector is sized to deliver approximately 4.05 milligrams of fuel with a 2.5 millisecond pulse or 18.13 lbs per hr at approximately 36 PSI. The 5.7L injector is sized to deliver approximately 4.83 milligrams of fuel with a 2.5 millisecond pulse or 23.92 lbs per hr at approximately 43.5 PSI. This information is typical for all manufacturers and flow rates will vary slightly even between identicle injectors.
Good luck and hope this helps.

replace the coolant temp sensor, not the coolant temp sending unit

have the converter checked it may be partially clogged

This solution is for 1987 to 1989 Chevrolet Camaro vehicles, TPI V8s.

It's an Idle Air Control (IAC) circuit failure. The close throttle engine speed is 125 RPM above or below desired (commanded) idle speed for 45 seconds. See a dealer service department for trouble diagnosis.