Thank you all for your input. I just would like to share with you the outcome of my overheating problem. First, yes it started to boiled after driving a while. I again took the radiator out and asked them to open the radiator to see if any cores are blocked. No blockage. I then changed the water pump although there was nothing wrong with the pump.
Dave you said: - “Removing the thermostat is not a smart move as the flow of coolant around the engine has now been altered”.
I then put the thermostat (74ºC) back and then took to the road. My overheating problem is gone. Thanks Dave.