Clutch slave began leaking and was unable to keep clutch disengaged when stopped. Needed a loaner, so took to dealer. Problem causing slave to blow was that clutch was way too stiff. RS4 clutch disk was worn out and lots of crud on trans splines. Car has 275k miles with about 200k on the clutch. I asked for RS4 clutch replacement, but dealer refused since car is A6.

New clutch and slave got car back on road. Noticed a bit of engine revving when disengaging clutch to shift on way home from dealer. Scanned with VCDS and found codes, 17866 P1458 Exhaust temp sensor bank 2 short to ground intermittent, and 17947 P1539 Clutch pedal switch implausible signal. This is not the clutch switch in the starter circuit, but the white one that connects to ECU. Dropped kick panel and found clutch switch not properly adjusted, so ECU thought clutch was always disengaged. Adjusted switch and that fixed engine rev overrun issue.

Drove car for a couple of days and EGT code came back after some full boost runs. Noticed some slight stutters at WOT. Rather than replace EGT on driver side, which is a royal pain, I put in a jumper wire from Blue wire red stripe on EGT Bank 1 connector over to Bank 2 blue wire in the connector. Left Bank 2 EGT itself not connected. ECU is now getting EGT signal for both banks from good sensor and car runs like new. I think the odds of bank 2 needing high EGT enrichment, when bank 1 is OK are very low. Dealer probably would have adjusted the clutch switch for free, but would have socked me for 2 new EGT's with their replace in pairs rule, plus a couple of hours at $150/hr labor.