I can't answer on behalf of a ZR1 owner, but assuming things are similar to LT1/4 cars I can tell you that the computer wants a balanced engine. If you increase your fuel pressure too much, it will compensate by shortening the pulse of the injectors... this leads to a bad spray, and less HP. The only way to increase fuel pressure is by testing the air/fuel ratio. PSI of the system really means nothing.
I feel like half the time the ECM is my friend, and the other half I am at war with it! LOL... I have just seen too many people put adjustable fuel pressure regulators on LT1/4 cars and lose power... they will just crank it up a few PSI, using a fuel pressure gauge instead of using air/fuel ratio... these guys are usually really confused as to why they lost power.:crazy