Noenav

Ok so my car had been running fine until a couple days ago. The car started sputtering and hestitating when I would hit on the gas hard. The car has trouble starting up the first time in the day. I can get it started by either hitting the accel or weirdly by disconnecting the injectors. Once I get the car started and let it warm up it will start up right away no problem. I recently rebuilt it with cam new opti wires plugs etc so it should be getting spark. It only hesitates when I hit on the accel hard or quick, it's sputters and hesitates like it wants to turn off and my rpms go down but once it catches up it doesn't sputter at high rpms. I changed the fuel filter and no luck. I also put a fuel pressure gage with the vacum line discconnected and it was below 40psi maybe around 38. I fired the car up and the pressure was around 35psi and drove around and the pressure seemed to drop to 30 when I would hit the gas wot and jump all over the place when it would sputter. Any idea guys could it be the fuel pump, fuel regulator or the injectors?

Injuneer

You test the pressure without the vacuum WITH THE ENGINE IDLING. Should be 43.5psi, but GM accepts anything from 41 - 47psi as within spec. Reattach the vacuum line and pressure should drop proportional to intake manifold vacuum. A drop of 8 - 10psi with a stock cam, less drop with a more aggressive cam.

Then take it out on the road - pressure should rise as you open the throttle, drop when the throttle closes and vacuum increases. Take it to WOT/5,000+ RPM - pressure should not drop below 40psi.

Have you scanned it for codes?

PS: Always a lot easier to help when you have a signature. Might want to add one.