Another option is ECU upgrade from chip logic. He did my bro's 135i and damn!!!! O.B claimed 70kw and 160nm gain that sounds a bit much but that car was a rocket, my bro raced a chipped m5 E60 and beet it 3 times out of 5 on the quarter mile, software alone. I think I'll go with what i've seen with O.B. Plus its undetectable well so i hear.