Originally Posted by CBVaughan

I fixed it!

So here's the update, for those who are curious, or to help those in the future, if they happen to have a similar issue.

After compression testing, leak down testing, and visual inspection, I made my diagnosis. There were obvious signs that the last mechanic who worked on this car was sloppy, if not incompetent. Screws were missing from the front bumper and the coil pack wire harnesses, the belly pan was missing, and two of the four plastic engine covers were missing. Also, I noticed white paint marks on the camshaft pulleys. With this information, and knowing how important it is to use the cam lock tool, my diagnosis was that the mechanic who replaced the exhaust camshaft in January 2013 didn't use the camshaft locking tool, and that the timing was slightly off. I pulled the trigger and ordered a camshaft lock tool off of eBay (approx $120 shipped). The tool arrived, and it was time to see if I had guessed right.

The tool went on to the left side fine, but it wouldn't go on to the right side. It went on to the exhaust camshaft, but wouldn't go on to the intake camshaft. It looks like I was right! Time to get the timing belt off.

So I basically did a timing belt service, but had to disassemble the right side without the lock tool on. As soon as I loosened the cam pulley bolts, I rotated the intake camshaft and got the tool to engage. Then I put everything back together. Also cleaned up a lot of oil on the front of the engine. My guess is that the hack mechanic didn't replace the cam pulley seals - but I did.

Moment of truth - time to start the engine. It takes a couple of turns to get fuel back into the engine, but then starts right up. After a few seconds, my wife, who wanted to watch the start up to see if the engine would explode, tells me she thinks the car is on fire. Smoke is coming out from under and behind the car. After initially being startled by the smoke, I realized that I had put oil into some of the cylinders when I was doing testing. I assured her that the car was not on fire, and that the smoke would only be temporary as the oil burned off.

I let the car idle for about 10-15 minutes, then took it for a drive. While not perfectly smooth (I assumed because the computer still needed to fine-tune the timing), it ran well. No CEL.

So now it's five days later. The car runs great! I've been driving it every day, and it's a dream. I was really looking forward to driving this car, and was getting frustrated watching it sit in my driveway while I decided where to spend my time and money troubleshooting it.

Total cost of the repair was about $200, most of which was the cam lock lock tool. Now that it's running well, time for basic maintenance and new RS6 replica wheels!

Thanks to all who gave advice.