So this morning, I reflashed the OE tune to the XPL0DR. I then updated the X4 with device updater, performed a factory reset to clear all existing information, re-confirmed update, loaded the new tune from Torrie, and flashed it to the truck.
A short 0-60 WOT data log is attached. Lambse and AFR values seem much more reasonable than before (to my untrained eye), so one of the things above seems to have gotten me back on the right track.
On a side note, the vehicle quirks when a tune is being flashed kind of weird me out. I always wait until all the displays and interior lights turn off before starting the flash process. When I first loaded the original 87 tune from Torrie, the airbag light and the BLIS lights on the mirrors were illuminated. When I reflashed to OE this morning, the airbag light and my interior color accent lights came on. When I loaded the newest tune from Torrie, only the airbag light was on - nothing else. Bizarre.
Thanks again for the help in getting me straightened out!