volvo v40 1.8 GDI no codes 4000 RPM limit OK from cold, bad after hot start.

Question

The car is perfect when started from cold. After warm up if engine switched off and then restarted the rev limit occurs.  Tests show the fuel is cut off at 4000 RPM. New throttle body, new MAF - no change. Fly by wire model, only other symptom is a bit flat below 4000 rpm when in rev limit state. Volvo main dealer says no light / no faults / no codes? Is this some form of limp home mode? Any ideas most welcome.