My 2003 trailblazer is having issues running when I put it in gear and accelerate I have replaced the motor,fuel pump,fuel filter,cam sensor,cleaned the throttle body,and computer. Will start and run in park just fine put it in gear will then go and stumble and stall. When I replaced the computer I was able to drive it for 44 miles and the issue started again. I cycle the key and I can't hear the fuel pump and it won't start. I then let it sit for short period of time then cycle the key and the fuel pump will work then I put it in gear and try to accelerate and it dies. I have checked the fuse box and switched the relay and it seems it has power. The fuel pressure regulator has no gas in the vent line. Any ideas I am at a dead end and have no more ideas