Swapping them over rules out, Connector Issues, Wire loom issues, human errors and DME issues. If an actuator is faulty the fault will "move" the other bank.
Ensure you know what bank is what. There is images on Youtube videos and the internet showing the banks labeled wrong.
Tricks You Can power the actuators "live" on your car.
1. Ensure Actuators and TPS connectors are plugged in
2. Key in Ignition - press start button twice (do NOT press cutch or break peddles to start the car)
3. When full ignition is on press the Gas/Accelerator peddle to operate actuators live. (two man job to see them move).
Tips
Your car is alive when un plugging units and reconnecting. The car will detect an unplugged unit as "a fault" and shut that bank down. I suggest resetting the actuators by simply locking the doors, waiting 10 seconds and opening the car again will re-establish COM's with the actuators. Some instances this may need to be done twice.
Connecting Rods / Linkages must be connected to the main throttle bodies. As the actuators talk directly to the TPS that is physically bolted on to the end of the 2 large throttle bodies.
TPS / Throttle Position Sensors: top right picture there are 2 connectors located where the Actuators sit; these TPS connectors MUST be connected, especially If your doing the above recommended test "Open & Close" accelerator pedal test.
Fault Codes Codes helps, Get Latest codes by a fresh scan. Check them against my fault code page. Every actuator code is listed.
Have you got the right actuators? There is a slight difference between M3 and M5/6. Pictured right is how to spot the difference.
Fault MOVED BANKS - After swapping Actuators
if the fault has moved banks and moved "with the suspected actuator". I suggest double checking the connector is fully pushed in, and check there is not something stopping it. Getting the latest codes, checking the above tips before you contact me. I would require and ask for original code (previous bank) and new fault codes after swapped banks.
Fault stayed on the same bank - After swapping Actuators
Connector / Pins Check that a pin has not been dislodged.
TPS as mentioned above, ensure both TPS is connected and double check its fully connected.
DME Resetting TBH I personally don't know how this is done, but I have had garages report back to me telling me they fixed the issue by resetting the dme.
Wire loom break Only ever heard of this once. very very rare.
Tips
TPS / Throttle Position Sensors: top right picture there are 2 connectors located where the Actuators sit; these TPS connectors MUST be connected, especially If your doing the above recommended test "Open & Close" accelerator pedal test.