1) Unplug MAF, try starting and see how it drives. Your car will run rich while its unplugged (more fuel)
2) Change fuel filter. If you haven't already, by your mileage you're OVERDUE.
3) Add 2 bottles of Chevron Techron (BMW fuel system cleaner)
4) Check Fuel Pump pressure.
5) Check injectors (Although Techron should help)
6) Check coil packs/sparkplugs
Do it in that order, the first items are free/needed anyways.