Go for CF wing mirrors or some interior trim in cf. Or go for bigger wheels. Or exhaust mods (they actually do make your car faster and sound great too). I could go on.... It's a question of $$$ I suppose. Have you looked at the mods options in British BMW enthusiast magazines (eg BMW CAR)? They're really good.
335i | 6MT | SG | Jade Grey | Poplar Grain Grey | 19" 230 rims | Sunroof | NAV with TV & voice control | HiFi | Sport Suspension | Rear Sunblind | 35% tints