I did buy the truck used and it came with the dual exhaust I wouldn't be surprised if it had a throttle body spacer. Any help on checking if it does? Where do I look?

 

My 04 has the same whine/whistle and its been doing it for 3 years.. after I changed the transmission it started doing it,, but everything has been ok for 3 years. It comes and goes correct ? more so when its cold but not just when its cold. Sounds like a turbo…

 

I've got a similar whine/high pitch whistle. Sounds like a turbo spooling. It happens very seldom, and it seems to be more so when the temp is below freezing. Happens all the time when the temp is below 10-15 Fahrenheit. I've never figured it out, as it only happens while driving, and it is unlike any belt, power steering, alternator noise I have ever heard, and it only does it under acceleration. I was concerned when I first heard it, but It hasn't gotten any worse in 3 years, and seems to have no adverse effects.

 

It doesn't sound like anything is broke and its been 90 degrees here in Iowa and its still done it