Well... over here mod'ing your car like that is highly illegal. You can get into a lot of trouble with the Polizei IF they ever stop you. Fine and Points! Plus... your insurance can deny a claim if you got into an accident and they somehow find out you modded your car.
I think Alpina offers a cold air induction box... butt they are really stricht on who they allow to order spare parts. You have to provide an Alpina VIN and give them a photos of the broken part... before they will "allow" you to order a spare part! Welcome to DE! lol
Most guys over here just do a flash tune and thats it. Maybe an exhaust and FMIC - as well. But its not like us crazy Americans are with P-O-W-E-R!!!