I had it in my M3 and it worked fine. It re-mapps the throttle response.
I didn't feel any change in the so called "lag". I Feel It's best utilized in non M3 e9x application where the drive by wire response or the lack of can be unnerving.
2009 M3 Alpine, carbon roof, Akra slip on.
2011 335ix, Le mans Blue, Black Dakota, M-sport, PE Exhaust, VMR VB3's, ZCP 359m's, JB Stage-2, H&R Coilovers.