I'm not real familiar with Audi thermostats but I know alot of american car thermostats already have a small pin hole. I have always thought that it was to allow a little coolant circulation past the thermostat. Otherwise if the thermostat had a perfect (or real good) seal it would not sense the coolant temp. as "cold" coolant would be trapped against the thermostat. Russ 87 5KCSTQ