Heater Control Valve
 

My car is an AUDI A4, B5,1.9 TDi, Diesel Turbo, Year 2000, AJM engine.
The previous owner has disconnected one of the lines from EGR value which goes in to a round unit below and front of the Coolant container.
This unit has a line in from top that connects to the EGR value and another line in at the bottom/side of the unit from the coolant container. I presume this is connected to the Diesel filter and this helps to cool the diesel before going in to the firing chamber.
I have checked the web and the closest identity that I could get was "Power Break Booster"
When the EGR line is connected engine enits white smoke and it appears as if the turbo is not working. When the EGR line is disconnected and the line is blocked, engine works fine.
But I get only 9 KM/LTR in Twon running and 13 KM/LTR in long distance running. As per the manual it should be in the range of 11 and 16.
Can some one tell me what this unit is called and whether I should replace it and if possible the part number.
If I go to the agents I will get fleesed and I do not hav that kind of cash. If I know what is it called I will be able to get it from singapore or Dubai where parts are more reasonable.
Over here private garages does not know what this item is called.
Will some one help me please.

well, Well, Well! Nobody even bothered to look at my problem.
But I have removed the part and found what it is.
It is called "Heater Control Valve"
The part Number is 4A0 809 809.
If this unit is faulty you get white smoke emitting from your exhaust. Temporarily you must disconnect the EGR line going in to the unit and close the line.
Once unit is replaced you can re connect the EGR line.