Low power and dies while driving

[j.dehn]

I have a cel but its only on when the truck is running. My friend checked it with the scanner he uses on his powerstroke tow trucks and the code didnt show up. I havent had a chance to take it anywhere else to have it checked. It runs and doesnt skip but is very low on power. Its only making about 8psi of boost. When I tow my jeep it dies occasionally but I push in the clutch and let it out the truck starts right back up. Any help will be greatly appreciated. The trucks info is in my signature.

Jason

[j.dehn]

I changed the cps and fuel filter today and it seems to be idling smoother but it still has no power. I also checked the oil so I could rule that out as a possibility.