I found the fuel regulator leaking and extended crank on start up, put a new gm regulator on and there is a grinding/restriction type noise from pump, fuel rail, and fuel filter. I put the old regulator on and its gone, so i thought the regulator must be bad, installed another new one and the same thing.

So i thought the pump must be going bad, i put a new gm fuel pump in and a new gm fuel filter in. Same thing.

If i unplug the vacuum line from regulator the noise is gone, noise is only at idle. Truck drives perfect even at idle when its making the noise.

Any ideas?