87 iroc z28 305 tpi...the engine was running rough with no power and would stall out sometimes in gear. Had alot of hestitation and back fired. I adjusted the timing and gained some power back. its alot smoother now. I put a fuel pressure tester on the fuel rail. The guage reads 3psi with the car off and the key on. When I start the car the gauge read betweens 40 and 50 psi. Would this mean that the fuel pump is junk? I already replaced the filter.

 

Your fuel pressure should be 43.5 at idle. Take your vaccum line off the regulator at idle and see if it goes up to about 50. Remember when you time it to disconnect the EST wire.

 

Could also be the regulator. When you pull the vacuum line off see if gas comes out the regulator. If so it is shot and needs to be replaced.