Muffler O-ring seal was fine...maybe I have too few miles for it to matter. I'm not hearing any unusual exhaust noise and I torqued it back up to factory specs according to FSM.
The hitch however was a real pain... it took me 4 hours at that and probably longer if I had not take the muffler off. I was doing it by myself so that didn't help. Good thing the garage door was closed as I am sure the neighbors would not have been pleased with the 4 letter expletives during the course of the install. The brackets that are used on this hitch toward rear of CX had so much paint in the screw holes it took me 1/2 hour just to clean the pain out so they would properly thread. It was one of those.. what I thought would be easy was hard and hard was easy...generally anyway. It is on there now and not coming off. I used painters tape everywhere along the bumper so I wouldn't accidentally scratch anything. Pulling the muffler off was pretty easy. I used some silicon based liquid wrench that was supposed to be safe on rubber. Using some floor jacks to support various things also helped.
I'll probably wait a week or two before I do the trailer wiring. I want go out at drive it and won't be towing anything for a while.
I do notice the Yakima rack does contribute to wind noise. I wonder if it would be noisier or quieter, while unloaded, without the front pane/deflector on there? I though I read someone say it would be noisier. It is definitely quite a bit noisier with sunroof open. The noise is not too big of deal since I generally have the radio up.