So I have the truck running and driving with the 6L In there. But I am having a problem at WOT. Driving around town its fine. Doing a WOT pull and I loss all power. Its like it up shifts to keep the truck under 3k rpms. In park I can rev the engine out but when there is load it just doesn't move. So far I have just replaced the FPR since it was the one that came with the engine. I do have a 450 in the tank and crazy fuel pressure at idle (78psi). Seems to stay there reving the engine. Cant see the fuel pressure while trying to do a pull. My first thought is the fuel pump but is there anything else that could cause this problem?