Well, this is not the update I wanted to write.

I got it all back together, cleared the codes, and then started it up. It cranked fine, and I let it idle for 15min or so to see if anything came up. No codes so I decided to take it down the road.

For the first couple of miles all was ok, and then with the cruise on it started to accelerate as I went up a hill. It made a single "thunk" sound, and I turned the cruise off real quick. As I was slowing down, I heard a high pitched tapping sound. As I slowed down and pulled over, it sound more like something flopping around as the rpms settled. Maybe similar to a rock in a can, high pitched and not a consistent rhythm.

I got the wife to come get me and the X5 so it's back home now. Using my stethoscope, it's definitely on the bank 1 side and when it made the sound on the road it did trigger the pre-cat O2 bank 1 too rich fault again.

I'm going to pull the air boxes off again on that side, and I wonder if I lost the bank 1 pre-cat. I've had a cat break up before and it did sound like rocks in a can. Or it could be the turbo I guess as well.

The only fault is the bank 1 pre-cat is too rich, and otherwise the X idles seems ok other than the rattle. Nothing else seems to be affected or seeing an issue. Figures.....lol