Goopster..
yes.. that is the GTP whining.. appearently you have never been at Desoto Speedway when the GTP clubs get together down there at T&T.. they are really loud and i have seen quite a few fast ones down there...

and for the record.. yes.. they do have an Eaton Blower on them.. atleast the 2004 GTP does which would lead me to believe that they all had them since they all sound the same and it would make no sense to change the application...

I got this from a website...

"Powertrain

The 2004 Grand Prix GTP is powered by a 3.8L V-6 with a high-performance Eaton supercharger that pumps out 260 hp (186 kw) and 280 lb.-ft. (380 Nm) of torque. Engine employs electronic throttle control (ETC) to provide no-lag engine response."