Unregistered

I was wondering if any one could help me on my over heating problem? I have changed the thermostat, water pump, hoses, had the heads check for cracks, new radiator and the entire system flushed.but still will run up to about 215 to 220 degs then back down to around 190. I not looseing any coolent or is it boiling over I put a mechanical temp gauge on it to rule out that the gauge was bad. beside that the truck runs strong any help would be greatly appreciated. Thanks