What bank was the O2 sensor on that showed a fault? If it was Bank 2, (that happens to be the side of cyl 2,4,6,8) then chances are that is your fault, as it's about the only thing that's common to those 4 cylinders, that could cause a misfire (if it's reading badly then the engine ECU will adjust fuelling etc for those cylinders, but if that is then wrong due to bad sensor info, the knock sensor will then detect a misfire).
I'd be trying to look at the live data from the O2 sensors - if one isn't responding like it should do, then chances are that's your problem.
The only other this it could be... and you'd be really unlucky... is if somehow all 4 HT leads to cyl 2,4,6,8 have been damaged and causing a misfire. Due to the design of the coil packs, the cylinders are mixed across the coils - so there isn't a single coil pack (or 2 in the case of a GEMS) that just does the even cylinders.
My money would be on an O2 sensor, or bad connection to it.