Maybe a bad coil? My '12 also has a *very* occasional miss... started noticing over a year ago (about 3k miles) and thought I would give it time to develop. It has not. Still very occasional, sometimes at idle, sometimes when I'm only just on the gas. Dealer was recommending MAF cleaning due to miles (70k) and I've seen it suggested in the forums, but passed on the service so far.
I do not think a passenger would notice the miss (the tech didn't either), it is really a single spark missing if it is a ignition miss. Really just a slight shudder or stumble to a otherwise smooth engine.
In other cars, I've been able to motivate a bad coil to act up by putting the car in as high a gear as possible heading up hill and lugging the engine... no luck with the M... so far
Are there specific ignition coils that tend to go bad on the 3.7? I know on some other engines (n52, 3.0 duratec) the ones up against the firewall tend to go first.
Been long enough that I'm getting concerned about plugging up my cats... thinking of just getting three coils and doing one side and then the other to see if I can find the culprit, but still not sure it's a coil thing!