What's the difference between these engines mechanically? Have they beefed anything up along the way to cope with more power? I'm thinking the 125i is really just a detuned "128i" done so, so the performance difference between that and the m135i is bigger.
Sure I know on a modded car, especially a turbo one you can turn the wick up all you want, but if my car is mechanically set up to be a "128i" and just detuned for marketing reasons.. Well I might be inclined to load software that gives me it's real potential