I envy you with all your modifying plans. Once i get going i do not stop. I have to confess that my 335i is in an advance state of tune and i doubt whether the new M3 will stand a chance even if it is tuned.
I have always loved tuning and modyfying my cars as a hobby. From my first datsun pulsar which i bought cash brand new for R15 000 in 1981. Can you believe the price! Nogal with my first study bursary money. Could not resist the temptation. I only gave that car away to a friend of mine early this year. Anyway, i tinted that car with an illegal black tint - i could hardly see where i was going. On university campus the car was known for being a "whore house on wheels". I do not know how the car got dubbed with this label, because i was really innocent! ha, ha...
I am fortunate that i only drive the 335i over weekends to have fun and when i want to hit the track.
My daily commuter is a 120diesel BMW which is also tuned to the hilt. anyway back to my 335i: I started with small interior mods like a new gear lever and small exterior changes. Then i replaced the standard air filter with a K&N filter. The HP and torque increased slightly (according to the dyno)but it was the sound that was the most obvious - a lovely throaty sound. Then I installed the AA xede from Active autowerke which transformed the car. I think you already checked our their website: www.activeautowerke.com
The increase and power is phenomenal. The third mod was the H&R race springs. The lowering transformed it even more. I got rid of the heavy BMW wheels for very light 19 inch deep dish alloys and very low profile bridgestones. The car behaves completely different to standard. I can only think of a nice afrikaans swear word to explain this to you but will behave myself. I wrote a review on this which is on this thread. Then i got rid of the first two cats and replaced it with riss racing catless turbo down pipes. The sound and power are intoxicating. I have also fitted some plasma boosters etc. I am still struggling to figure out how to combine the xede tune with a custom tune, but will eventually work it out. I followed a similar process with the 120d but kept the suspension stock on the 120d and it's been 3 years and i have not had a single problem. Nothing has broken or had to be replaced. Of course BMW always had something to say when the car went for it scheduled maintenance, but i listed all my mods in the waranty book and havent had to pay for servicing. I think if something had broken they would probably have blamed the mods. I know i am now talking all over the place but the thing i absolutely enjoyed about tuning the 120d was the day that i understood how the common rail turbo system worked and of course finding the signal running from the ecu to the turbine. (hidden) Needless to say the possibilities in raising the boost and playing with the timing of the opening of the electronic wastegates became great fun. The 335i is still new to me but i am getting to know the engine, its workings and components and i am convinced the car is capable of so much more. Especially when i look at those two small turbo's! But it is not only about releasing all its ponies it is also about how the car looks and behave on the road in the twists and corners etc and of course the howl of the straight six. I am planning 4 more mods for this year on the 335i - An intercooler, replacing the second cats with freeflowing cats, a decat exhaust and the new BMW steering wheel with the race meter. But the Rand must streghten against the dollar a bit more. Having said all of this if someone with a new M3 want to swop with me i will consider it seriously, but would only be able to give up the 335 for an hour or so.