Turbo whistle

It sounds to defiantly be a boost leak. Check the charge air cooler hoses and clamps. You would be surprised what you can miss take a closer look. Normally wouldn't make noise on a bob tail if any because it's not under a load but as soon as there is weight on it,it will whistle

 

If it's sucking air around a clamp or something you can idle it up good an squirt either around the clamps. If you hear the either change the sound of your motor then you found your leaky clamp.

 

in my case it was turbo actuator

 

Check the exhaust manifold. If you see any black spots you may have a cracked manifold seal.

 

A good spray bottle with soapy water is your friend. Fill it and spray the whole boost system with the truck idle bumped up. Your system will probably only be making 3 to 5 psi while idling. If you see a bubble, imagine what it would be like at 30 to 40 psi.

A scan gauge is not a bad investment. Just don't be upset if it won't read all the gauges you want it to. If your truck doesn't have a sensor for the ECM to read, your scan gauge wont read it either. Case in point, on my 9200i with C13, there is no sensor for the exhaust temp. So, I will eventually have to install a pyrometer if I want one.