Originally Posted by jagman
Great documentation! I recently got an 08 E92 M3 that came with the Akra slip-on. I've contemplated the Akra midpipe but the Akrapovic midpipe would have smog implications in CA. The Challenge Street X-Pipe was recommended since the primary cat stays in place. I see from you that requires welding. I was hoping to do the install myself... that might not be possible. How is the drone now that you have had it a while? Also, have you considered the ESS tune with the cold start mod for that drone?
Thoughts from anybody for that matter?
As GTM indicated, you do not need to weld and may use the clamps but you will need to cut the rear extension of your OEM primary cats to install the x-pipe or it will not fit. Welding definitely is the cleaner and (to me) aesthetically the better solution.
The drone was noticeable in the beginning. After 4k miles, the drone is still noticeable (but very seldom) at 2 -3k rpm and cold start. I have grown used to it. The Akra Slip/Challenge Street x-pipe combo is definitely one of the quieter setups out there.
I have put some thought into the ESS tune. Maybe sometime in the near future!