About 3 months ago, I purchased a 1990 Pontiac Firebird Formula for my 16yo son. It's a 5.0L TPI motor with an automatic behind it. It has developed a problem. At highway speed, it runs horrible. It won't get out of it's own way. It seems to hit a wall at about 2300 rpm. At first I suspected a bad fuel pump. I checked pressure at the rail and here's what I found. The book calls for 37-43 psi when first energizing the fuel pump. I have 40psi. It then calls for a 3-10 psi drop when the car is running. At IDLE I have about 37psi. I checked for proper flow and that is fine. I ran the gauge under the hood and to the cowl so I could watch it while driving it. The car cruises at 72mph 1700 rpm with about 37psi. When you get in it and try to accelerate, the gauge is all over the place. Pressure varies from 35 to 52/55psi and on occassion, hits 60psi. As soon as you get off the throttle, it stabilizes again at about 37psi. When I brought it back home, it was ideling in the driveway in park at about 37/40psi. If I blipped the throttle to rev it, pressure would jump to about 50psi and then return to the 37/40psi as soon as the idle came back down. I think the regulator is bad and needs replaced. What's your opinions? Thanks in advance for your help.

 

might wanna replace feul filter, as general maintence. its located beside the back of the driveshaft drivers side. not sure about your iregular jumping of feul pressure... but it sounds as if your engines being starved. does it rev fine with the car stopped? like does it hit a wall per say?