I downloaded Shigeru Tanaka's P51D Mustang Aces from the library (stpma.zip). What an awesome machine to fly! It handles beautifully, looks and sounds great. However, sometimes about five minutes into a flight, the engine audio develops a high pitched noise which I can best describe as though the treble is over modulating. This carries over to the ATC audio. I have not encountered this with any other airplane. This is a minor annoyance to an otherwise outstanding file. I have a new computer with plenty of power, but I only have the basic onboard audio chip/card. Any ideas?

Thanks in advance.

Bruce Keyes