thats a possibility, is more of a whining sound? is the truck harder to start after it warms up? and do you have and check engine codes? when you say power loss, how much? not as touchy as use to be, or having harder times building boost, which is indicative of lower fueling pressures.I have an 04 3500 and my lift pump has started making noise when i switch the truck on and i have noticed a decrease in power and fuel mileage. Could it be going out?