Originally Posted by bdaddylo
Most performance exhausts are loud at cold start up. The 1M does NOT have an exhaust flap. Check realoem.com if you don't believe it. The flaps that are found on some BMW models are all vacuum controlled. The additional sound is exhaust drone which is usually louder under load.
It is not that I do not believe, I just wanted to confirm before I keep looking for a vaccum the doesn't exist lol thank you very much for providing a source it is much appreciated .
I guess the next issue would be catless vs stock...