The high temps here in the southern US are not likely part of the original design protocol for the V11 mapping. I can sure feel *it* when the temperature, air density, and barometric pressure match perfectly that day in Mandello when they were happiest with the test motor!
Good advice from Hubert, as always. Yet, he and I will likely disagree on modifying the right head temperature sensor holder. I found significant hot weather 90˚F/32˚C - 95˚F/35˚C) improvements after lowering the mass of the holder.
Better to start with the CO, maybe a high quality fuel system cleaner (like Techron), "comfortably loose" valves, air bypass screws cleaned and set a full turn out. Simple stuff that I found helps my hot weather running.
(EDIT: yes, a MG shop can very easily set your CO. Mine was delivered at minus 27. HUGE difference after it was set to 0)