I installed an Air Force one intake on my 4.6 lit 2003 F-150 along with a Poweraid throttle spacer and a Jet performance chip. The gains are impressive but the engine is making a hissing noise under hard aceleration. At first I thought it was a high pitched squeal like a belt slipping but it sounds like air now. Is this normal?

 

That's just the air moving through the TB and swirling in the TB spacer. I've got the same intake setup, and mine whistles like there is no tomorrow.

-Flea

 

Does the throttle body spacer have any positive effects on performance?

I've heard both good and bad about these.

 

Nothing worth the ~$80 they usually run. Save that for something like a chip.