My RS6 had 178,000 miles on it when the wiring harness that runs between the engine and the firewall caused the ECU to fail and cratered cylinder 2 and 7 due to pre-denotation. The problem was discovered after installing new short block. The Audi dealership mechanic spotted the harness having damage like some of the other Audi's and VW's he has seen in the past. He cut it open and the two of the main leads had shorted together due to the sheathing cracking and falling off. The new harness has two of the main wires with newer sheathing technology. I highly recommend checking the harness for heat damage. $1600 part can save you about $24k in a rebuilt engine.