i have a 89 camaro rs it was originally a 5.0 5 speed, and now is a carb 377 with th350. when i start the car it runs fine and the fuel pressure is at 6 to 6.5 psi, once it warms up though the fuel pressure drops to 4 and stays there. then if you try to go drive the car it runs like crap. it is the stock electric fuel pump and is still run off the computer which i think is the problem. im just lost on what to do and check anymore. i tried to find a wiring diagram on the fuel pump so i could just put it on a switch and just eliminate the computer but i couldnt find anything. if anyone has had an issue like this before or has wiring diagrams or any info on what to do it would be greatly appriciated.

 

4 PSI would not cause a problem with your carb.
If your fuel pump was a problem it would be because the pressure had gone too high - over 8 PSI. and your carb would be flooding your engine because of it.

"runs like crap" is not very descriptive of any symptoms in particular, so it's hard to go from there.
Is it misfiring or surging?
Is it still running the computer controlled distributor?

What type of carb do you have?

 

the fuel pump was fine before i did the swap and it was hard enough to get the pressure to 6 psi so i know its never been to 8 psi. once it warms up it goes lean and will start to knock. the distributor is run off a msd igintion. the carb is an edelbrock 1405

 

What fuel pressure regulator did you use?

 

Well first, a lean/knock condition isn't normally caused by a pump not delivering enough fuel to the carb, but is caused by the carb not delivering enough fuel under load. But, just in case, whenever the lean/knock happens kill the ignition and put the car in neutral, pull over and remove the carb air-horn and inspect the fuel bowls to see if the level is extremely low. Then you will know if this is caused by a lack of fuel delivery from the pump or not.
Usually when a pump isn't keeping up the engine will hit a wall of hard surging/stumbling when under load.

An MSD unit can be hooked up to either a computer controlled distributor or a non-CC distributor, so that doesn't answer the question about the distributor. The distributor could be a major player/cause in this problem, and so it is very relevant to determine exactly what type distributor you have, and how it is set up, especially since you indicated knock.

The 1405 is a little on the small side for a 377, but you should still be able to make it work ok.
Have you checked your AFR with a WBO2 while loading the engine?