Originally Posted by slowturbo
Dumb question, but how do we know without getting under the car whether or not we have the n51 motor?
Under your hood you'll see a emissions sticker. It'll state "SULEV" for N51 cars and "ULEV" for N52. You can also go to realoem.com and input the last 7 digits of your VIN.
FYI...N51 cars also have the 3-stage intake manifold and slightly lower compression ratio along with some other small differences.