Originally Posted by Especial86
If its a "whine" that sounds like its coming from the driver side when in the cab then its your alternator.
Ive had that sound before, But that happened at idle as well. This is more of a Rat-ta-ta-ta-ta-ta, Im leaning more toward Catalytic converter. Truck has 177k on the original cats, and i went through the whole plug/misfire issue 2 years ago.
ALSO this does not sound like a warped manifold, been there, done that haha