I set mine to 78mph. It seems that it is best for still passing cars, but yielding good mpg's (35 or so). I found even going 80mph, the mpg drops a bit.
Mods: AEM Meth Injection, BDP downpipe, Wagner intercooler, Bilstien B12 Kit, M3 Control Arms, MB Quartz Kit/Alpine Amp
Best 1/4mi: 12.34s @ 111.88MP/h