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The second problem is thet the car goes sometimes in limp mode ("engine power reduced,...")
When it is in limb mode, the sound jumps are not anymore.

When it goes in limb mode, ist ALWAYS in P500 mode + full throttle and more then 7.000 rpm. Its courious that the problem is ALWAyS: idle contriol unit; SMG CAN BUS OFF (CD8B)

It doesnt make sense because the idle Control Units are not used at full power and there are 2, but no specification which one it is

I checked and cleaned the throttle acturators already, but they seem to be ok , and I checked the wiring of the idle Control Units,

Can it be that one of them is defective and makes that unusual symptom?
One of your idle actuators is faulty, I have had to replace both of mine due to the exact same symptom. To confirm, if you have ISTA you can run an idle actuator self test. This will tell you which one is broken. I bought mine from https://www.bmwautoparts.net/en/catalog/part/13417834495/0/idle-control-device as they are much cheaper than the local UK BMW dealer.
Rockauto also sell the actuators, my first one came from there at around £300, but last time I checked they were closer to the £700 my local dealer wants.
I replaced one actuator when it failed, after I guess 10 years of use. Then a year later the other one broke.

Replacement is a simple enough DIY, whilst you are in there, it would be good to check the throttle actuators. Mine were a little rough/uneven so I bought a replacement gear kit from https://www.rebuild.org.uk/ and swapped the gears over.

For the surging issue, I still have this after changing both idle actuators. I would be interested if you find a fix!
 

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Just rang Bmw for a solenoid price they are pretty much £1000 each! They were about £300 a few years back - I’m hoping the surging isn’t that
 

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Thanks - I am curious how eagle gets on first - is it possible that the actuators are the problem for surging at all?
 
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