I'm stuck... Bought a 2006 Z4 about a year ago with the n52. I just finished redoing the front suspension on it and now I'm looking for some more horse power. From my understanding the difference in the n52s from the 3.0i to the 3.0si is just a tune? I had thought maybe the n52 for the 3.0si had less magnesium because everyone seems to think if you add 1 more horsepower to my engine you'll blow the block out or something lol. If this story that the 3.0si is just a tune is correct, what stops myself or anyone from getting that tune and making up the gap? / Where can I get that tune and make up the gap?