Sometimes when I speed up or even take my foot off the pedal the engine makes a whistling noise for a second or two ,,,, is that the turbo or what. Is it something to worry about. Never heard before. 2006 F250 6.0.

 

Have you checked all your boots? I only say this because I had this issue on a Peterbuilt I was driving last week to haul corn. It didn't do it all the time but when it did it was LOUD. ended up being one of the boots coming off the intercooler.

 

Another possibility could be the Y pipe and a crack in the expansion joint. If it is there should be signs of soot on the firewall or back of the engine.

 

Thanks , I will check on those things this evening when I get home and let y'all know Thanks