I have a LT4 and am having hard starting when cold. Something is letting the fuel pressure leak off while sitting. I've replaced the fuel pressure regulator, when it's vacuum line failed the sniff test. I deleted the fuel pulsation dampener yesterday..............no help. Does the fuel pump have a back flow valve in it?

 

Yes the fuel pump has the valve. If you have to cycle the key 2 times to get the pressure up you need to replace the pump.

Nate