This does sound like a lifter might be on the way out... this happened a couple of years ago to K-Man S... after the usual reading out of the DME for over-revs, etc. they covered it under warranty. I believe they replaced all the lifters on the bank that the failure occurred.
Here's a couple of links...
The full thread:
Bad Lifter / Engine Repair - Latest News
The dealer covering it:
Bad Lifter / Engine Repair - Latest News
brad