I have an 05 F250 which I drive only in the summer and even then not that much. Just coming up on 20,000 miles. Recently when you accelersate to between 20 and 40 MPH and let off the accelerator quickly, it sounds like air coming out of a bladder. I took it to a Ford dealer and they said it had to do with the turbo, and that it was fine to drive as is, but if I wanted to make the noise stop, I would need to replace the turbo which they were prepared to do for $2,000 or so. I would appreciate any thoughts on the cause and perhaps a less expensive solution.