95 Z28 missing..?????
You may be dealing with some code issues after replacing the opti & rotor with some 'fine' tune needed.
Sounds like its running way too lean so you need to keep the rpms up so it won't sputter.
Also, when is the last time you changed the plugs. With the rest you may also be looking at a valve not firing properly - you have a batch fire not a sequential fire so you'd notice it at lower rpms on sequential vs batch.



