I have been having some problems. l ll start with the engine. 95 T/A LT-1, MM6. New O2 sensors, cleaned and flowed injectors, new IAC,TPS,MAP, plug wires, plugs. Computer programmed by Fastchip. Full length header 2 1/2 dual exhaust, Flowmaster 40 series. This is all put into my 76 Camaro.

So here is the problem:
The car runs poor when cold. Crank it and it starts right up. It will idle smooth and fine, but give it some gas to let out the clutch and it stumbles. When it starts warming up (only a few minutes of driving) it is perfectly normal.
In between shifts, I get a single, loud backfire out of the exhaust. From what I can tell, it sounds like it is coming from the right bank. I am also on my second set of cylinder heads and this happened with both of them.
Once the car is warm, if I shut it off for 20 minutes and then try to starts it again (run to the store) it will have to crank for about 5 full seconds to start. Throttle position does not seem to matter.
Any help would be greatly appreciated as I only have one guess. Opti.
B

 

could be the opti getting ready to take a crap or Running very rich.

 

Check the fuel pressure when the engine starts, runs for a little while and then is shut off. I'll be curious to see what the pressure is when you shut it down. The pressure should hold for a good long time.

Also since you installed the engine in a different body, check to see where the fuel line runs and if it is close to the exhaust in any areas.

You are either getting a large air pocket in the fuel line (unlikely) or the pressure is bleeding down when the engine is turned off. We all get that problem from time to time.