I have an 05 with 98k miles that here lately have been having fuel pressure problems. I called a Diesel mechanic and he said it sounded like I had got some bad fuel so he told me to try changing the fuel filter. I have gone through three fuel filters and three full tanks of full and I still am having problems. Here is whats going on. When the engine is first started it runs fine I am seeing pressures of 22k to 20k at 70 mph but once the engine gets to normal operating temperature the pressure drops as low as 8k psi and there is no power if I try to accelerate. I am using a Quadzilla to monitor pressure. I am hopeful that one of the diesel God's can tell me what to look at or try other than just throwing parts at it. I still have 2k miles left on the warranty and the dealer said the high pressure pump is covered but the lift pump is not.

 

pull your Quadzilla then see if you still have the same power issue

 

Tried that still have same problems.