Z4 3.0si (same motor as e90 330i). I've gone through few different configurations but here's some videos of my initial setup: Supersprint headers + Burns Y-merge + 3" piping with Vibrant resonator & Flowmaster muffler:
Cold start-up
On-track
Since then, I've added a 100 cell hfc and swapped out the Flowmaster for a Magnaflow. The car sounds less raspy with deeper tones. I'll try to upload a video next week.