Have LS1 that started running hot. New thermostat, radiator flushed, new water pump, heads have been gone thru. Computer shows left head temp at 188,189 running down hi-way, climes to 210 at idle, Temp gauge on pass. head shows 193 on hi-way, then at idle it climbs to 240. New sending unit on the gauge and also shot the temperature on the gauge sending unit. At idle you can run RPM up to 1500 and temp comes down 195. No water boiling over or any leaks