My car runs just slightly past the center mark and is stable there with the 88C thermostat.

As I have a constant pinging issue in high ambient temperatures (on our 91 octane premium fuel) from 2000 - 2700 rpm under light load that several shops gave up on finding, I thought I would try a slightly lower temp thermostat. I heard that they are made, but cannot find one.

Originally the car ran slightly to the left of the center temp mark, but not with the last 2 thermostats. Water pump is new, car is well bled, front fan has been replaced, as low speed died; as I said, temps are stable there even in high ambients.