When some magazine tested it a while ago it wasn't any faster than a regular GT 'Stang.
Weird how halfway through the last corner the driver decides to actually press the gas.
You should check out the Grand Am Cup then. The Mustangs that race in that series are the real versions of this car. The "GTR" was just the show car version of the race cars to show the "Cammer" engine. Watch one of those races, and you'll hear that rumble every time.