Your missing the point. Any 15-25 year old car is going to need pretty much all fluid carrying lines and systems either replaced or rebuilt regardless of who built it. This is a fact. I've done six of these from four different brands and all are the same. Since German cars like Mercedes and Porsches have these very unique materials and complexities they are worse. The Porsche 959 had systems in it in 1986 that some cars are just starting to be common. All that tech and more is in even those old Porsches and you can see repairs like you describe for the Audi as common. I did not do the Porsche because when i looked at the cost and talked to the old time mechanics it was a money pit. It was cheaper to buy a four year old certified pre owned. Remember also the Air cooled mean all those systems are subject to even more heat than a water cooled system. My XK8 is rock solid and pretty much has been. It just costs money to change out the things that wear with age. Any 2000 and on Jaguar are not all that bad. I've had far more issues with Mercedes built things. I'm trying to warn you based on actual experience.