The real question is, what to do to complement the RS4 cylinder heads. My current thought is to shoot for something in the 550whp range on the smallest turbo I can manage to hit that goal with on pump 93 octane fuel and a water/methanol injection system.
After getting the car back on the road I discovered a slight vibration that would start around 40-50 mph growing more noticeable as speed increased to 60-70 mph. It was unaffected by varying rpm. I started troubleshooting with a trip to a shop to have the wheel balance checked. That did not eliminate the vibration. I then took the car back to the shop that routinely works on my car, HB Motorwerks, to see if they could diagnose the problem, their assessment was that it was related to the driveshaft. I hate this type of troubleshooting where expensive and time consuming parts need to be swapped out. At the moment I have a re-manufactured OEM two piece driveshaft being delivered from Wholesale Import Parts. While I’m hopeful that this corrects the problem since if it doesn’t it will mean buying additional parts and more work changing them out, if it does turn out to be the Driveshaft Shop single piece driveshaft I’m going to be irate at wasting money trying this driveshaft.
Finally some progress has been made toward getting this S4 back onto the road. The DMV inspector came out today and gave the car the thumbs up, I received the repaired title, now I need to get it registered and have a state safety inspection performed, along with a much needed alignment. Then I can begin the process of working out any remaining bugs.