When I cold-start, until it calms down (30-60 seconds, I think) there's quite a lot of cabin noise. I also tried turning off my MDS when I was testing out the resonator delete (before they straight-piped back out to the tips) and it got really drony at certain cruising speeds. But it seems fine now except for the cold start - I guess with MDS on you're usually cruising with 4 cylinders and everything quiets down.