No sorry, the photo is the original system for the E36 M50 325
The E46 M54B25 325 has separate pipes all the way back but with the pre-cats and 4 O2 sensors (pre and post for each bank) in the manifolds. It also then has post cats further down but no cross pipe, just a mid section resonator and the back box. This one is stainless all the way
RealOEM E46 325 Front Section (top pic)
RealOEM E46 325 Mid and Rear Section
I don't have the little vacuum valve that dampens the noise at idle
The E46 M54B30 also had straight pipes but without cats in the manifold so just 2 O2 sensors before cats under the car. These then go through the cats under the car and merge into one pipe that goes to the back. This one is a mix of weird size mild steel pipe at the front, stainless in the middle, then mild on the single pipe back. I assumed when I first saw it someone been doing some dodgy cheap repairs it was that untidy, until I looked on RealOEM.
RealOEM E46 early 330 front section
RealOEM E46 early 330 rear section
When they stopped using the weird air pump you see on some early E46s this changed to a system the same as my E46 325
The M3 has stainless all the way, proper 6-2-1 branch manifold with the pair of cats under the car with a balance pipe after the cats. It's separate pipes all the way to the back. Who knows what happens in the massive back box though before the four tail pipes emerge
RealOEM E46 M3 front section (bottom pic)
RealOEM E46 M3 backsection
The M3 retains the air pump from the earlier cars as not having pre-cats it needs to lean out the exhaust to get the cats under the car up to temp quickly on first start up.
It's this mix and match that leads me to believe they spent much more attention on noise levels, cost and emissions regulations than performance so my straight through 6-2-1 (but shorter) with a 200 cell sport cat and twin back boxes 'should' only affect top end performance in a positive way though it may well have moved the torque curve a little.
I wonder if the air pump would now be considered a 'defeat device'? It's certainly a waste of engine bay space.