The subject has been disussed in some threads recently, so: Since the temperature managment is so poor in the Q4 and the temperature often goes too high maybe this could be a solution:

http://www.daviescraig.com.au/Electr...s-content.aspx
http://www.daviescraig.com.au/Contro...s-content.aspx

A digital controller with an electric pump which reduces required power in most cases, do the pump work more efficiently and has the ability to increase flow if needed. If that doesn't help maybe a fan with higher capacity might help. I discuseesd the subject with an alfisti who has worked as an Audi mechanic for many years and he said that the radiators available today are far more efficient than the radiators available 15 years ago. I don't know. Maybe a new radiator from a car with the same power rating could do miracles?