Truck pulls fine in low RPM range, but when it turns up to around 2200 and above, it loses power until you let off the gas, and it will start pulling again

 

What year model and still running the stock lift pump? Start with a new fuel filter first.

MikeyB

 

04.5, lift pump replaced 15,000 mi ago. Injection pump replaced today, along with fuel filter. Truck has 87,000 mi.

 

Still does it with a new pump and filter? Is the lift pump the newer in tank design or the old canister mounted unit?

Another possibility is the high pressure relief valve is leaking under high pressure.

MikeyB