Can't figure out what is wrong.
AMB overheats each and every time.

Radiator is cold, and heater blows cold.

I assumed stuck thermostat, so put in new. No change.

I gutted the old one (took the spring etc out, so both outlets are open): No change

Then figured that coolant is going path of least resistance (with gutted thermostat) and instead flow down to bottom radiator hose, it just goes up to the hard pipe and to the engine.
So I blocked that path. No change.

Some reported blown headgasket or cracked block and blow combustion gases into the coolant without the big white smoke tell tale sign. Ran 'combustion leak test', no combustion gases in coolant.

With upper radiator hose disconnected with engine running, there is coolant flowing out of the end of the hard pipe.

Bled (bleeding screw on top of hard pipe) several times, including with raised reservoir.
Warm up with reservoir open (burb out).

Coolant temperature sensor (green, 4 pin, cross over pipe back of engine) shows about the same values for both measuring circuits (VAGcom reading in insturment cluster and engine module).

ANY suggestions what I can try?
ANY ideas what might be causing the overheating?

 

Over-heating an engine can cause serious damage. Have you checked the coolant levels now? See any leaks? If the radiator or other part in the cooling system froze, chances are snaptube vidmate it's sprung a leak (ice expands). Get this addressed before more damage occurs.