Sorry you are having this problem (and haven't gotten any responses to your first post). I had a similar problem with my '15 and it turned out to be the driveshaft. Has your dealership offered any explanations or even tried to diagnose?
Mine pings with anything less than premium. My '15 did the same thing. I don't want to have to use premium all the time, but I'd rather pay the little extra than worry about more serious problems.
You can also get the differential bushing inserts from Steeda and you probably wouldn't need to replace the stock bushings.
https://www.steeda.com/steeda-s550-mustang-adjustable-differential-bushing-insert-system-urethane-2015-ecoboost-555-4443.html
I get valve rattle on mine with anything less than 91. I'd love to be able to run 87 in it, but this car just doesn't like it. I didn't see any performance difference between the two, but could definitely hear the valves voicing their disapproval.
This is what I was gonna suggest. I live in Davie and work in Boca-- 30 miles each way. I petitioned to have them let me do 10-6, which helps. Mostly in the morning though-- evenings can still be busy but I'm able to take the turnpike instead if I need to.
Our local Mustang club was asked to display some cars at the Miami International Auto Show this week, so I agreed to put mine in there for the week. Nothing special mod-wise, but shows well in that light.
Bringing this back from the virtual grave-- I just noticed my front wheels don't even have the dust/grease caps on the hubs. Anybody else not have them? I ordered some today but was just wondering...
I got a set of black ones from eBay that were actually OEM and came in Ford packaging. Painted them gray to match my wheels and painted the dot Velocity Blue. Came out pretty decent-- dot looks better in person than in this pic.