All I could find reference to on BMWUSA.com was intake, exhaust and tuning for the engine. However the 330 is heavier, so something has to be different.

Why not get the 325 and spend the savings on good aftermarket components? When they come out, of course.

iirc, the 330 has 40 more hp and a number of features that are options on the 325 are standard on the 330.. the 13speaker stereo, 17" vs 16" wheels, HID lights, power & heated seats, and a thing or two more.

larger brakes on the 330 too.

You could "save on the 325" but to make it a 330 would cost more then the 330 and you would lose your warranty.

not to mention the 330 looks much better imo

Buy the time you tick the option boxes on a 325 to = a 330i you have bought the 330i but with the slow motor.

Buy the time you tick the option boxes on a 325 to = a 330i you have bought the 330i but with the slow motor.

Not true. My site makes this sort of comparison fairly easy--I'd say easy, but it's not possible to get the wheels and brakes the same, and I don't adjust for these. But if you check of the boxes that are available, you'll find that the 330 is still a nice even $3000 more than the 325.

The 18s on the 330 make the look of the car for me. But I must also admit that the seat of my pants doesn't feel a huge difference between these engines. The 330i engine doesn't feel as quick as it is.

When I test drove an 06 325 last month the dealer told me that it uses a detuned version of last year's 3.0 engine. The engine didn't run as smooth as I've come to expect in inline 6, so it leads me to believe retuning the engine could be relatively inexpensive and yield a pretty good power gain.