VW polo Thermostat

[yanna-man]

I have a G reg VW polo which continually stalls. The temp gauge never goes above half way, and if i put on my heater the gauge drops even further and the stalling gets worse.

I have put a piece of cardboard infront of a portion of the radiator which obviously increases the temp of the engin , this seems to help the situation somewhat.

The engine does seem to Rev quite high.Do I need a new thermostat or look elsewhere for a remedy