Originally Posted by Myaddiction
All the N54's have the same hardware. The only difference is the the 335is Z4is and 1M have a very mild tune from the factory.
Not really. There are some slight hardware changes...
The 335is/Z4is/1M do have
different (primary)cats. They are more free flowing than regular N54 ones. These cars also have the PPK(extra radiator in the passenger fender, higher wattage radiator fan, sound generator and SW tune from BMW) already installed along with a different flywheel and clutch - which the normal x35i cars did not get.
The 335is/Z4is/1M cars do have a special SW tune that also allows for over boost in the low to mid range for short periods.