So, time for an update regarding this problem. My friend found a broken valve spring last summer so the car has been standing in his garage until recently when he decided to change the springs. But until this happended we never managed to solve the problem with the strange and random engine cut outs.

But we're now 99% sure that we have found the problem. We can't say 100% because the car is still in the garage. Remember that we tried "everything", changed a lot of parts that we borrowed from a garage, measured all sensors etc. But now when the engine is out of the car we found a thing that everyone had missed.

The main ground cables behinde the generator were loose!! They are critical for all the power in the car and the bolt that holds them to the crankcase was gone. So the cables are only hold in place by their own weight and stiffnes. So a little bump or whatever would cause them to move around. This cable/connection is very hard to see with the engine in the car and everything in place.

This also feels like the "correct" error becuase the car used to run perfectely and suddenly this started, and I guess evertyhing was OK until the bolt disappeared.

So this could be a thing to check out for all you guys that have a problem with the engine cutting out or hesitates.