Water pump 997 cup question
 

Is there any water pumps difference beetwen 997 2006 and 997 2009 cup cars?
I have 2006 plastic impeller version and people say that there is a modification to metal impeller. I have overheating problems in the water temperature and I have replaced the radiators, the thermostat and the engine looks OK (no pressure in the water system).

Please help me if someone had a similar problem

Thanks