I did a ecu tune and the magnaflow x pipe , the pipe is great mod I actually feel more pull that I have put in . I got a makeshift intake kit coming in a few days from one of the members . Other than that you can do headers . Obx makes a set I'm thinking of getting but there are sets made by all the Benz tuners . You can Also hi flow cats and if you have the dough you can have a remote mounted turbo done . Lots of suspension options out there too .
OETuning. Check em out. Jeremy will work wonders on your car. He's pretty good with the BMW community as well. I've ridden in one of my friend's cars that he had tuned. The before/after was astounding. I'm looking to get mine done once I feel the need to splurge. :3 After today though, I'm guessing it'll be pushed back seeing as I need to get my rear bumper fixed.