Yesterday, I had the SuperSprint X-Pipe installed on my '03 M5. I wanted to share my experience with those of you considering this mod.
I only swapped the resonator, the exhaust and headers are stock.
The plan was to:
1) Cut the stock resonator out in the appropriate places
2) Expand the exhaust inlet pipe to accept the SS X-Pipe outlet
3) Use clamps at both ends to fix it in place
The process took a bit longer than expected because of the following issues:
1) The tubing expander the shop had was not strong enough to expand the stainless steel exhaust pipe, so they removed the mufflers, took them to a local exhaust shop and had them expanded
2) They could not find a clamp sleeve the right size (they thought the 740 clamp might be right, but it was too small), so they ended up just welding the rear junction.
3) The built in clamps at the front of the SS X-Pipe didn't seal the front joint. They are tightened all the way down (no gap left) and it's leaking a bit at that joint.
I'll be returning to the shop to get the front joint welded.
Hindsight is 20:20. If I were to do this again, I would remove the clamping section from the front of the X-Pipe, weld it front and rear and be done with it. No Clamps, No possibility for leaks, and cleaner install.
For those of you who are considering this mod...GO FOR IT! It sounds good, looks good (if you crawl under the car as often as I do), and does help, IMO, with throttle response. The sound inside the cabin didn't increase much under normal cruising conditions (comfort for passengers) but I can really hear it when I start pulling hard...
Thanks to Mark (MAH) for giving me the peace of mind that it wouldn't deafen me (more than I already am)
Thanks to North Bay Bavarian (who did a great job on this) for being patient with me while I looked over their shoulders and told them how "I" would do it.
Oh, one last note...keep in mind that this mod may be illegal in some areas for highway use