I just bought the '17 MKx 3.7 FWD in May. After a few weeks I noticed when I'm accelerating harder to merge into the Freeway, a few seconds later we smell the rotten egg! I never notice the smell any other time. I read a bunch of TSB's about the issue. beside the Cats, a lot about the vortex (behind hatch) sucking the smell into the interior.
Any ideas, beside new Cats?