The original brass mounted radiator can better be replaced by an aluminium version. More and quite expensive, but it allows your engine to run much cooler and more reliable. Even on Cosworth engines with over 300 HP!
The best tip given to me was that the Audi engines require an ALU radiator instead of the standard brass version. This because of the catalic process in the difference of the metals killing your cylinder head gasket. Even stronger recommended on Cosworth engines, because the gasket contains other materials. Mechanic claims this is the main reason of Cosworths being sensitive to popping out gaskets!