This morning prior to taking the pictures of the spark plugs, the engine was running very rich. It was so rich I was getting about 6400 rpm on the ground. When it was leaned out I was getting about 6900 rpm. Yesterday when the high end was leaned out it was getting about 6900 rpm but the head temp was about 290 degrees (on l/h side) after landing.

I am running the standard BME mufflers.

Is it normal to see up to 60 degrees difference between left and right head and won't the engine get damaged running that hot?