Lack of power

The car will only rev up to 3-4000 rpm, then it feels like a rev limiter comes in.
This happens in park or on the road.
This car had been to a local BMW agent who had put on a new coil, told the customer that they didnt know what to do from there. It then spent 3 weeks at another local garage where about 40 hours was spent trying to find this problem.
Parts changed already, Cam and Crank sensor, CTS, AFM, o2, exhaust dropped to rule out a suspect catalytic comverter and more.