For the last few months I've noticed anytime I accelerate and let off the gas I hear like a whistle sound (kind of like a sneeze) its hard to describe the sound but definitely seems to air escaping . Any one know what this could be?

 

I believe that would be your wastegate. I'd get it checked out.

 

Umm no, wastegates work when you're on the throttle. They open to allow exhaust gas to bypass the turbo compressor wheel to control boost pressure.

On the 11-12 motors there's a recirculation valve built into the turbo housing that let's the compressed air back into the intake piping when you lift off the throttle. They are vacuum and electric controlled.

The 13+ trucks use a blow off valve built onto the intercooler to do this.

It could also be a PCV line that is off.

Check all of the vacuum hoses and air lines to make sure nothing is disconnected. The recirculation valves have a rubber diaphragm that can tear. They can be easily replaced for a few $$$ each.