Originally Posted by
kane gray
Exhaust leak. Which unfortunately could mean cab off repair.
I wouldn't think a leak, beacause he said when he floors it it goes away. If it was a leak, I would think the whistle would get louder with more pressure...
Just speculating here, but maybe a turbo bearing? That is what happened in my 6.0. It would make this whisteling sound... needless to say I had the turbo rebuilt.