Infrared temp gauge reading off the plug basically from a fixed point/distance being the hole in the body shell, it's going to take the same reading off that spot regardless of the head, and from memory I also did readings off the engine block to confirm, engine did run 'considerably' hotter trying to run the old Mugen Ninja head.

Someone on the day told me the Ninja heads were not real great, I think the only reason they worked on the GRP based engines is someone also told me they ran cool...