fuel problem

[braggent]

i have a 96 chevy 1500 with 305 engine automatic ,i was wondering if any know how to tell if a pressure regulator has gone bad or is weak. .is there a test to check it or is it not checkable? i have notice that when i fill up on an empty tank there is no air pressure release when i open the fuel cap before i would always hear it when i open it . i have change the fuel pump about a 8 months ago and the fuel fiter 2 weeks ago. i have notice that when i turn the truck off there is a release sound coming from the engine like if some kind of pressure was release. not like a vaccum leak but a pressure leak. the only thing that i do remember is that after i change the fuel pump my truck after runnning about 10 min lack power and the rpms drop it would not do it all the time but now it is. if anyone has advice let me know.