A week and no response from the OP?
When asking vague questions you should try to post what you do with your car and what your intentions are. If you bought the car cause you liked the way it looks at it's fast enough for you then that makes it easier to focus on cosmetic changes. But if you want to take it racing then there's a new focus that you would want to go with.
2008 135i - Cobb/JB4, Spec 3+ Clutch/Flywheel, MS DP's, Berk street exhaust, AMS IC, UI CAI, CDV delete, Quaife LSD, M3 control arms/Links, RE Toe Link, ECS Trailing Arm, M3 rear SF & Trans bushings, SS brake lines, Michelin PSS.