This is one of the few real power delivering mods for the E92 M3, combined with race gas I think this is good for ~30 hp. It is a primary cat delete, leaving the secondary cats in place. I bought the Turner cat delete pipes:
https://www.turnermotorsport.com/p-3...elete/?pdk=AQE
Then welded (pro exhaust shop) them together with an appropriately trimmed factory exhaust midsection. This makes for a easy one piece swap in/out replacement for any potential inspection/compliance issues as cat delete is not emissions kosher. It also gets rid of the somewhat hack-ish clamp. So the mod is fully bolt on and easily/fully reversible. This definitely adds noticeable power and improves sound, louder and better tone in my opinion. Still not too much for a daily driver.
As you can see the pipes alone are $350.
Funky pictures are from their storage spot in my garage ceiling. Took two pics to get the entire length. Last picture is the original Turner pipes.