Changed Fpr, Now Truck Stalls Under A Load

[jpmire]

I have a 96 Silverado 5.0. I changed the FPR due to the truck having a hard time cranking when it was warm. Now I am having a problem with the truck running. It will run fine for a little while until I put it in D or R. In N and P it idles fine. While I am driving and come to stop it will hesitate and drop in RPMs to around 400. If I don't give it the gas, it will kill. Second problem is, when I turn the AC on, regardless of if it is in gear or not, it will do the same thing. I have changed the fuel filter out already. Thinking it could be the fuel pump but not sure.

[txab]

You need to get a pressure reading for your fuel pump to find out if it is the pump