2003 Bmw M3 2033 M3 Engine Sputtering Attempts Choke Cylinder Two

Problem: I have 2033 M3; the engine is sputtering/attempts to "choke" as in a cylinder or two are misfiring. The "Check engine light" comes on after a while and sometime it goes off because the problem happens intermittently. The first attempt to repair it was by the BMW dealer, and the say it was coil #5, which they replaced. After 200 miles of running, the same problem returned, so I took it to another mechanic that specializes on German made cars. They said it was the #5 fuel injector (after replacing some of the electrical harness to the spark plugs/coils) they replace the Injector. Two days later, the problem returns and I take back to the same Mechanic/shop. They said it needs replacement of the two fuel pumps - I said are you sure that is the problem? And they said yes- so they replaced the fuel pumps. However, after 150 miles, the same problems returned. The car is at the same shop and being tested; first feedback I get now is the possibility of a cylinder leaking compression, or a defective main ECM/ECU. I have spent $900 at the Dealer and so far over $1800 with the second mechanic. Can you provide your thoughts, recommendations and advice? And how much a rebuild ECM should cost? (Mechanic said they probably can't get a new one since the stop making it after 7 years from the manufacturing today of the car)
The Fault codes provided by my mechanic are:

206 Misfire Cyl 2 without Cyl Cutout

208 Misfire Cyl 4 without Cyl Cutout
209 Misfire Cyl 5 without Cyl Cutout
210 Misfire Cyl 6 without Cyl Cutout


213 Misfire Multiple Cylinders without Cyl Cutout
31 Fuel Injector Cyl 5