I'm still not convinced any of the coils were "bad" as I did enough swapping between working cylinders, and the problem kept staying isolated to cylinders 4 and 8 (4 primarily). Also, I replaced the spark plug in cylinder 4 two days ago (and they then went and did the same thing. It makes me think that cylinders 4 and 8 were allergic to what was installed. Makes me wonder if they had re-programmed with what was in there, if the problems would have been solved.
Thinking about the conversation I had with one of the service advisors, he said that misfires often cause problems in their paired cylinder - so 1 and 5, 2 and 6, 4 and 8. I'm wondering if the plug/coil in cylinder 8 was the real problem, causing a misfire sometimes in cylinder 8 but more in cylinder 4. As the plug they pulled from cylinder 4 was clean (since I had just installed it a day earlier) but the 1 from cylinder 8 was a bit dirtier.
I'm thinking I'm going to sell now and find something more fuel efficient.