[moveswiftly]

Wow someone comes and gives an honest review about the 1m and his experience with heat soak and you guys treat him as if he's trying to pull some elitist crap?

Get over yourselves guys.

I track my 135i with the SAME engine as the 1m. Also have Catless downpipes, intakes and other performance mods.
I have an LSD, Coilovers and part ///m suspension.

I also am putting an intercooler / methanol injection.

I can tell you for sure. After 3-4 laps and temperatures going above 250-260 you will DEFINITELY see a noticeable decrease in power. If you don't you're either
A. Running lots of Meth to keep the engine very cool and have dual oil coolers
B. Not pushing your car hard enough to feel heat soak
C. Not very attentive to the way the car responds and drives.

At the end of the day the 1M is still an N54 powered 1 series with lots of carefully engineered suspension package (Fenders, Suspension components even LSD).