Installing E90/92 M3 Sosi X Pipe

The Sosi X-Pipe replaces the OE resonator and secondary cat x-pipe to make the exhaust a little less restrictive and provide a bit more power, 10-15 HP/TQ are common dyno improvements seen when replacing the OE x-pipe.

Standard Disclaimer: ANY USE OF THIS INFORMATION BY YOU IS AT YOUR OWN RISK. I ASSUME NO LIABILITY FOR YOUR USE OF THE BELOW INFORMATION.

Prep:

First step is to get the car up on four jack stands. I usually do this by driving the front of the car up on ramps:

And using the rear central jack point (rear subframe) to lift the car and place the rear jack stands under the rear side jack points:

Then doing the same using the front central jack point (pad under subframe) to place the front jack stands under the front side jack points- the ramps provide room to get the jack in place:

With the car on jack stands there is plenty of room under the car to see and work. The first thing removed is the front spacer/clamp using a 13mm wrench to remove the two nuts on top. Clamps can be slid out of the way to be removed with the X-pipe later or they can be flexed around and off now. I did not see a way to reuse this once the Sosi X-Pipe was installed so it was left off:

I picked up an exhaust tool set from Advance Auto Parts using their loaner tool program. The only tool used for this was the exhaust pipe cutter. I tried to cut as close to the weld as possible to have enough pipe to clamp the Sosi pipe on to but this caused clearance issues with the cutting tool, you will probably need to allow at least ½” to have room to cut in front of the weld:

Or you could use a Sawzall/reciprocating saw to cut the pipe, I had to finish my cuts with one of these since I started the cut too close to the weld for the other tool. When the cutting is finished, the pipe will still be held in place with the center support and rear clamps:

The rear clamps are removed next using a 13mm socket wrench, the bolt will need to be unscrewed almost all the way for the clamps to be released:

The four bolts holding the center support to the car are removed using a 13mm wrench as well and the OE x-pipe is removed from the car:

Comparing the Sosi X-Pipe to the removed OE X-Pipe:

Installation:

The two nuts are removed from the center support using a 13mm socket wrench and the center support is installed on the Sosi X-Pipe, the support welds should face up towards the car:

The new pipe is installed by placing the rear sockets into place and loosely installing the clamps and the front is slip fit over the cut OE pipe. I used some exhaust paste to make sure this was a solid and leak free connection. I found it beneficial to install the provided front clamps prior. After the front clamps are installed and tightened, the rear clamps can be tightened and then the center brace is reinstalled:

I found this to be a subtle change- the sound is a bit more racy and the power seems to be up, the weight should be a good deal less as well. For the cost and results of this mod I think that I would do it again since I have no plans to get software and remove the primary cats. If I had planned to do both of these things I would most likely have done the Turner test pipes/ESS software and left the OE resonators and secondary cats in place.