I've been driving E46 M3s over five years now. How is that possible when an average carfreak changes car every second year? This car simply combines many of carfreak's ambitions into a single package. It's a smooth cruiser in town, but with just small adjustments it transforms into a decent track tool.
This car has been tuned by Kelleners Sport. It has the Bilstein PSS9 coilover kit tuned by Kelleners, H&R sway bars, Brembo brakes, Kelleners exhaust, some engine adjustments and also various bits and pieces of carbon fiber tuning for the looks. What I can say.. it's the suspension mods and the brakes which make the biggest difference over a stock M3. Kelleners' exhaust is just great for the sound alone, especially if you happen to love sound of the M3 - like I do.
For people who track their cars I can strongly recommend front camber plates or other ways to increase front camber. This relatively cheap modification saves your Beemer from dark shadows of understeer and restores lively driveability which was designed by BMW ///M, but in the end sacrificed for the sake of "safety".
Surprisingly I like SMG2 gearbox mainly on track, where it leaves driver's hands more attached to the steering wheel. In slow traffic SMG2 can be a little jerky, especially with downshifts. Luckily SMG version 3 in M5 / M6 has improved significantly on this area.
I feel my K3 is quite ready now. Some chassis fine-tuning will always follow, but that's about it. Should I change or should I stay? Either way, I think I'm quite close to what a true carfreak's vehicle is about.