The Hamann Thunder was featured in Bimmer magazine which was a 325i or 328i totally reuilt with M3 everything and a 550hp V10. They only had 0-60mph which was 4.3 or 4.2 I believe and then went on to say that traction, weight and aerodynamic drag were the limiting factors.
That car did have 305s on the rear.
I'm wondering how much of an improvement a supercharger kit will be? I supercharged my 330Ci and that was a huge difference. I'd hate to spend $10k+ on a marginal improvement. I'm sure it would help rocketing out of tight corners on the track but what is the use if you can't put the power to the ground?
DISCLAIMER: I just read this...really not an expert on this.
2013 F30 328i Melbourne Red
2011 E90 M3 Monte Carlo Blue
2004 E46 M3 Imola Red