Wierd vaccum on rad
 

Intake full of oil
recently overheated and the radiator had to be replaced in my 07 2.4 L4 pt cruiser. Since this happened the car has coded multiple misfires and stalls at random. The car has had timing belt replaced 500 km ago and thermostat and rad are new. Water pump is working and no oil in coolant or coolant in oil. The car is still losing coolant somewhere and overheats still. I changed the plugs and when the upper intake was lifted I found it was full of oil I found the plugs covered with oil and the electrodes on 2 had evidence of coolant contamination. My thoughts are the head gasket is bad, can anyone help with this. I do not see excessive exhaust and it is not blue or white. The cooling system is developing extreme vacuum that is collapsing the hose and it is very hard to open the rad.

The radiator cap is supposed to relieve the vacuum as the system cools down. It should be replaced, but probably that's not the only source of your problems. There are dyes that you can add to the coolant that show up under ultraviolet light. They are used for the purpose of tracing leakages. You might want to consider that to find the leak.