After checking all the usual suspects such as cooling system problems,timing and guage accuracy look at the spark plugs or co2 reading to see if a lean fuel condition is the culprit.Many times lean fuel and to much timing will cause an engine to run hot.Also make sure you run a thermostat or restrictor(usually a 5/8 hole) to allow the coolant to pass through the rad slow enough to be cooled.Don't realy on the engine supplier's opinion unless they have actually investigated all the circumstances.All the possible issues mentioned should be checked and eliminated.