Basic steps on how to do the OEM exhaust mod on a 2008 BMW E92 M3 yourself. SPOILER ALERT: We aren’t professional welders and the welds are not pretty. It makes zero difference to the performance or function of the sound. If you are welding this yourself like we did, just make sure there are no holes and it’s welded up good. If you want the inside of your exhaust to look pretty then take it to a shop that will probably charge you $500 to do this. I’ve compared this mod to some other aftermarket exhausts on the market and I believe this sounds better also.