Sorry for starting another MCSF thread.
This fault started appearing shortly after having a new idler and tensioner fitted for the auxiliary belt (still not sure if there's a connection).
Once the revs get up to around the 3k mark, the rev counter plummets and the car starts to kangaroo. The yellow engine light is lit and shortly afterwards I get 'Master Control System Failure'. If you keep your foot in it this will continue, but let off and the faults will clear until you increase the revs again. Obviously this is a real danger when overtaking, joining a motorway etc.
shows what's going on from inside the car. You can get the idea from the first minute of video (sorry for the jerkiness).
No faults are recorded making this pretty hard to diagnose. I see that people with similar faults have found a bad earth to be the issue, but the difference in my case is that no other gauges are affected. Three spark plug recesses were found to be filled with water, but sorting this made no difference. Coil pack impedances have been checked, although they're still on my suspect list.
I'd really appreciate it if anyone could give me some pointers. My next check will be MAF sensor, but after that I'm a little stuck.