I had been under the impression that the UrS4/S6 has a turbo I5, while the S6+ has a 4.2l V8. In an old auto motor und sport issue, I saw one classified ad for an S4 4.2 and another that listed an S6 4.2 as well as an S6+ 4.2. Which is it? If they all had (optional?) V8s, what's different about the S6+? -gbr