There is no misfire & revs remain steady, applying throttle there is no hesitation the pick is clean & powerful, (just luv the torque of these engines- lovely) there is no loss of power right through rev range. The issue appears to clear after a long high speed run.

Engine parameters are very good for a engine that has 123k behind it and are @2500:

lamda 1.006, HC 0, CO 0.026

Occasionally a "lumpy" idle @ 850

If this was a carburated engine I would have said fuel starvation as most likely culprit.

CO only recorded @ 0.005%