Sorry to hear of the problems with the S4. I've recently bought a late 2011 S4 sedan... and almost to scared to ask what the problems were...
regards
Just think maybe it had a hard life, Was ex Queenstown so maybe ski field trips/gravel roads..
Everything was pretty well worn lots of maintenance stuff, brakes way past what I would let them get, exhaust flex joints long past it expiry date (wire was actually frayed and could see its internals), headlight faults, indicator faults, alignment out all worn on the insides probably due to the lowered springs, was getting CEL codes on the secondary air pump (wires were corroded and shorting out), temp sensors bla bla bla.
Add to it the Cam chains and torque converter had also been done recently it had a small (well large) fortune spent on it.
Did try to reach out via VASK to the place that last serviced it since they are a member and and was only a short period of time since last service, but they never replied.
The dealer was willing to fix it all but I not a patient person at the best of times and didn't have the time to muck round swapping cars out while it went back and forth getting fixed each time.
Its still for sale and the last time I was at the dealers picking up some paperwork it was back in for something else to be fixed..
Warning to anyone looking don't touch it!
I do now have the performance itch that needs scratched so currently looking at importing a B8 S4 Avant