It appears it could be water either in the spark plug wells or the cam timing sensor. My car does it cold and hot. The other reports were only when hot. We did have mega rain for a couple of minutes yesterday.
Now it gets too 5500rpm before going funky.
I tightend up the screws on the throttle body to make sure there wasn't an air leak. I reckon the gasket has gone.
Aaah well, got some instant gasket in the shed to try