I've posted in this room about a massive backfire after highway driving.

https://www.thirdgen.org/techbb2/sho...hreadid=196934

I started into some diagnosis as per the Pontiac service manual. I have a Fuel pressure guage on my rail and noticed that after initial prime and and/or engine start, the system will not hold pressure after shutdown or I turn back the key. So I went throught the test. When I came to the step of pinching the return line off to the tank, the pressure held. Since doing this the pressure is continuing to hold. Its an adjustable regulator. Can this be the source of my trouble?

Thanks

 

The pressure always bleeds off when you turn the car off and doesn't build up again unless you restart the car or turn it off for a long time.

If you have an AFPR, your pressure could be too high and cause the symptoms you describe. If your engine is stock, stay within 5# of stock setting. Either way, if you go too high you will basically flood the engine or freeze the injectors open.. That point depends on the calibration of your prom and brand/condition of your injectors....