I apologize. I just went back and reread your post and see that you changed the thermostat twice. But you also said that it onlt runs with the thermostat that you drilled a hole in too. That's not good. Are you sure that the thermostats that you tried are good? 195 degree thermostats? 160 degree do not allow cooling down properly, especially in the higher temperature electronic ignition egines. You could still have a bad head gasket or a crack somewhere, like a head, BUT that will cause overheating, and you WILL see built up pressure in the cooling system. If it is NOT really overheating, you could have a monitoring/metering problem that is causing some sort of safety to shut down. I guess that you really need to figure out if it really is overheating or not. Not losing coolant like blowing it out the exhaust? Not overheating because not leaking, losing, or blowing coolant into the overflow?
The thing that gets me, is that you say it will only run if you insert the thermostat that you drilled a hole in as a bypass. That's not a metering problem. That would suggest to me a need to relieve pressure and force cool coolant into the block, and I would expect to see physical overheating beyond the meter telling you that its hot. It also suggests a bad thermostat that is not opening, and now uses the hole you drilled in it to flow coolant at the same time it doesn't allow the radiator and fan blades to do their jobs. Those two thermostats you tried, you are sure that they are both good 195 degree thermostats? Try flushing the system, another new radiator, and if it still OVERHEATS beyond just saying that its running hot, go after the head gaskets IF you are sure that the water pump is good, and it sounds as though it is.