[Keith]

I posted this on P-T as well because I'm just desperate for an answer. Do any of you guys have a clue as to what might be going on? I definitely appreciate it!
Myself, along with some very experienced people are having an issue with a car we cannot figure out. To start, it's an 88 camaro IROC-Z that was bought less motor/trans to be a fun car to test stuff on and to beat up a little in the process for the sake of numbers. Currently the motor is slightly worked 355 backed by a TH350 and run to some 4.10s. The issue we're having is with the fuel system. Because it's a retrofit carbed application, the pickup in the stock tank was modified and then checked twice for clearance in it's appropriate baffle and we capped all lines going into the tank (total of 4) except the vapor return line, which we attached a breather to, and of course the main feed line. Main feed drops approx. 14" down to a filter, then holley blue, then aluminumn line approx 6', another filter before the regulator set at 8psi, then to the Edelbrock 750. With the exception of the fuel tank line and the aluminumn line and it's connections, everything is stainless braided and uses -6an. The problem we're having is after the car has been running for about 1/2 hour, regardless of how we treat it, we start loosing fuel pressure slowly but surely. Doesn't matter if it's WOT or idling, we loose it at about a PSI every ten minutes, the only constant being the car running. If we shut the car down and then restart, it just picks up where it last left off. If the car cools down completely, it's starts right at 8PSI and stay's there until about a half hour again. The car has been through three fuel pumps, two regulators and a completely re-done fuel system including a different carb and the same problem no matter what. We checked voltage to the pump at the pump and it doesn't change and we upped the car to a 90Amp alt just to be certain. It just doesn't make sense because it's not temp related...we could cook it as soon as it fires up and the temp could be holding at 160 and then pump won't crap out until about the 1/2 hour mark. The only way we know is the A/F gauge starts going hot and sure enough we've dropped down to 5 or 4 PSI.
I'm sorry this is long but wanted to give you guys everything to scratch your heads over. Everything in the fuel system has been replaced which would indicate that it's not the fuel system but we're all miffed over here. Any suggestions....questions? Thanks guys...