I also tried the unplugging of maf and got trans failsafe mode. Mine 2001 x5 3.0 121k. Sort of the same problem that i just resolved. A little opposite than yours. Would start up and run great but when it finally heated up, about 10 or 15 miles into drive, it would suddenly feel like it was running on five cylinders. I could pull over turn off start back up and it would run fine until i put a load on it, punch it or begin an uphill climb. Then it would revert to running like crap but could pull over turn off restart and fine again.Stealer did find one bad coil and told me intake exhaust cam sensors were faulty. They were aftermarket bwd. Took them out and returned to oreillys where they gave me 2 new ones. Still same prob. Took them back and they refunded my money and went directly to bmw oem brand. Installed and problem resolved.

Next up changing out leaky oil filter housing gasket.