unplugging the battery has the nice side effect of erasing the transmission control unit memory, the radio presets, the obc time, the dash memory, and probably something i forget. its also easier to unplug the DME harness.

resetting the lambda map should fix the lean warm up, but the o2 sensors could be fouled, and will get iffy again. either way, your car will run better with a reset.

i am extremely curious as to why there was no MAF failure check engine code, as lack of continuity seems like a hell of a good reason to throw one!

also, change your oil, its probably diluted with fuel and not protecting your engine anymore.