Just looking for anyone else's opinion before i start wrenchin. I beleive i have a bad fpr.... so far this is how i've come to it... (The only mod done to the truck is light efi tuning. But is returned to bone stock right now.) Truck runs fine with a light pedal, very light pedal. but any time i roll into it a little, somewhere around half throttle the truck feels like it detunes and is starving for fuel. Once in a while it will throw the Low Rail pressure on PE. Running the EFI Scan software i can watch my fuel pressure, comanded and actual. The fuel pressure is normal at idle, and when driven lightly will climb up to the 20k+ range, like comanded. But the second i push the pedal a little further, the truck, "hiccups" and detunes/ rail pressure drops to around 10k psi, And stays there still i let off completely. Runs normal when engine op. temp is below the 160ish range. Soon as she gets warm i start haveing the issue. Any Ideas? oh and the odometer is at 102,000. Isnt that a B****?

Before anything how is the fuel filter and air filter.
fuel filter will cause it too starve.

Fuel filter was replaced less than a week ago. That was my first thought. Just about thru my second tank after replacing the filter, just incase it was dirty fuel... no avail. By the way the truck is an 05. Thought my signture would show up...

What about the FPRV? I just replaced my FPR and it was a waste, wound up being an injector problem. Now I have a good but used FPR in my shop and a new $170 on in the truck that works the same.

I was going to say the same thing (FPRV). Mines getting lazy and a new one or shim kit is on the list when I get home from deployment. My truck does that as well, its good up to about 85 - 90 mph and then it almost falls on its face. Well that and it could be my weak tranny not holding it either...one of the two.

Installed shim to fprv. Fixed the problem! at least for now... we'll see. Was cheaper than buying a new one to start off. Thanks.