Wincey

Hi. Newbie, first post so be kind.
MG TF 135. Starts ok, runs well when cold, pulls throughout rev range.
When warmed up, misfire at 2000rpm, intermittent misfire/loss of power at 4000rpm. Ease throttle, power returns reluctantly.
Fitted new plugs, new coils, new cam sensor, changed throttle position sensor, new MAP sensor. According to diagnostics, O2 sensors are both working.
Any thoughts/suggestions gratefully received.