96 Chevy K3500 with the 5.7l It has about 215K miles. I am trying to diagnose a fuel pressure issue. My truck first started to run rough like it had a miss. Check engine light came on. I had codes for both banks being lean. I cleaned the MAF sensor with no change. I checked for vacuum leaks. I hooked up a scan tool and checked the LTFT for both banks. They are both at 25%. I hooked up a fuel pressure gauge to the rail test port. Key on engine off it is around 45. As soon as the pump shuts off it almost instantly drops to 0. I am trying to figure out if I have a bad check valve in my fuel pump or if my FPR is bad. Before this all started, I noticed a loss in power. It could barely get a trailer up the slightest incline.