Hi all!
I own a '98,F150,XLT,EC,4.6,5 speed,4x4,OFP.
Within the past two months I have noticed a slight knocking sound from my engine compartment when I run the engine over 3000 rpm. This is especially annoying when I am climbing or passing. I can press my foot further on the gas and the noise will become slightly louder, and it becomes nonexistant with the clutch in.
I just had my 36,000 mile tune up today and I had a tech ride with me on the highway to verify the problem, so I could get it covered by warranty.
After looking onto the problem the tech ordered me a new air intake sensor. He said that should take care of it.
I would love some of the opinions from the experts here. : ) Or see if anyone has had the same problem.

Thanks.