I think you’re pretty much spot-on justincredible. The catalysts are really the weak link here but mostly because it’s engine-out to change them. Audi really screwed us with that move. If I spent whatever it’s going to cost for the SC kit and my cats blew out a week later, I might not be too happy. So I understand the conservative tune.
I’m assuming there will be a “plus” tune for cars with cat-less headers but I’d also like to know what the fuel situation is, whether the stock HPFP’s flow enough fuel or are they very close to being maxed out.
On the piston rings, they’re identical to the R8 and they all do quite well with turbos and superchargers. I believe I read a technical document a while back that everything was forged, pistons, rods, and of course, the crank.
On the transmission, the DL501 is strong enough to handle lots more power. The stock clutches are good for 800Nm and there are aftermarket alternatives. I’m in a DL501 chat group that mostly tackles problems with the transmission and it’s about 75% S6 guys. Heavier car, more hp, but many of them are making 700 to 800hp. And it’s still the same problem, the mechatronic, not the gear set. Sometimes it’s worn clutches and you just have to wonder if that is because of failed solenoids and not being able to maintain adequate clutch pressure. But it’s mostly the same as the RS5’s gearbox, different clutch part number and different clutch plate. I haven’t checked to see if the gear ratios are the same.
The ZF8’s are not bulletproof by any means. They overheat too and can have differential issues. But it’s a ubiquitous gearbox used in many different makes/models and probably has a lot more aftermarket support.