If this is the cause, now I'm wondering..., I'm at 168k miles and the Dinan S2 work was done when I bought the car used in '05 at 42k. ????

15 more minutes to 8am until I can call my dealer.

Unless you recently had work done on the car, I kinda doubt if this is your problem since it had held up for close to 9 years.

Yep! It was not the gasket.

Seems the transfer case disintegrated taking the front drive shaft with it. All without a whimper or a bang. Approx $4400 to repair including tax. About half what a new tranny would cost to install.

My siblings are asking me if it is time to get a new car. I lamely replied my car is getting new..., piece by piece.

Looks like the end of next week I'll get it back. Newer than it was!

When you hear hoof beats, think Horses.
 

This is one time when it turned out to be a Zebra. Thanks for the update. My X5 has not had any problems since it sucked that "rubber gasket, '0' thing". Incidentally, I glued it in place.

The throttle body was one of the parts replaced with the Dinan S2 work. So I kind of figured it would not be that.

I've had to replace the water-cooled alternator with a lifetime warranty Bosch a few years ago. (which begs the question "why did it not already come with it?") The gasket between the engine & transmission 2 yrs ago. The oil separator exploded last Christmas as I had been only doing short drives, thus not allowing the water to dissipate but instead froze taking out the separator and a valve cover. Valve gaskets replaced 3 yrs ago along with the valve cover gaskets. Replaced the steering wheel with an M5 wheel and the nav & phone were finally yanked out 4 yrs ago and replaced with the Alpine. The tail light assys were replaced, but not with LEDs as they were not available back then. I polished the headlights with the 3M kit and protected them and the front with a clear bra, just replaced this year after 8 yrs of use.

Angel eyes are still on the bucket list, though immediate needs have pushed this further back.

Still trying to figure out how to bring back the black anodized window parts. She's still looking good at almost 14 yrs old. though I bought it used in '05. This car fits me. Especially as I describe myself as "having Jackie Stewart desires in a Reggie White body". Driving should be fun, not boring.

A more definitive way to determine if it is a fix is too look at the Short term and long term fuel trims. From your DTCs it appears the engine was running rich. I would never rely on the fact that the SES or CEL hasn't come back on as a fix.