Intermittent power loss at 4000rpm

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.

Does it have fresh fuel? The E10 in my TF has degraded badly over the winter lay up I think.

Yeah, fresh fuel, even treated it to some Redex, for what that's worth.
Good thought though. Thanks.

I had a similar problem with my car it was the pre cat 02 sensor. I'm not sure but I think if you disconnect it and the problem goes it's the sensor.

Hi Bob.
That thought has been going through my head. When I first got the car last autumn, one of the many, many jobs I had to do was replace the front exhaust section which meant moving the sensor from one pipe to the next. Pig of a job and it did take some punishment to get out.
I'll give your test a go later.
Many thanks.

I'd love to say problem sorted, however not so. Disconnected pre cat sensor, car ran rough from the start and got worse as it warmed up. Not to say it's not the sensor as it's obviously effected by temperature.
Back to the drawing board sadly.
Nice try Bob. Thanks.

New O2 sensor, same problem.
Now thinking vacuum leak or fuel pump. Looking at the plugs it's runnng lean.
Any thoughts out there.????

Sorted??? Hopefully.
Fuel pump!!!. Replaced the pump, not full assembly, just pump. So far so good. Performing well throughout rev range.
Happy days.