Woohooo I did 2:15 time!!
I recommend TC level 1, Bilstein suspension, ABS on. But it's hard like hell to go under 2:15 with keyboard. I visited the M3 challenge forum. There are also lots of freaks with momo racing wheels, even installed racing seat, big screens, dolby surround etc... Nothing for "normal people" like us, but some of them manage to do 2:10 laps!!! Of course, with the wheel and the equipment you can improve about 2-3 seconds, but there's still place to improve for us (2:13lap with keyboard maybe...)
Here a crappy video of my hotlap http://www.youtube.com/watch?v=mdpt2nb9Eho