I've witnessed the HPF Stage M3 on the Dyno and it is absolutely wild. That being said, I truly believe 340hp to the wheels in a 330 is going to be the limit to keeping the entire car reliable. Even with that, a better clutch will be needed.
I drive my 330i a lot and it never gets boring. I haven't been able to justify spending the money on a FI kit... Especially since I'm about to give the car to my soon to be 16 year old son. I suspect I will replace it with the Twin Turbo 335i, but the E46 is a much better looking car.
Lucky in Love, Life, and the Ever-after!