The Voyager Omnidekkas have an updated engine compared to other versions due to them being N270UDs rather then N94UDs, though I'm not sure if the one that's receiving the engine from the ex DFDS one will still be the same emission level, as it's an older engine maybe.

Nontheless Percy Main seem content with using the Long Omnidekkas on the DFDS service still, I did note they have extra grills around the exhaust system, so probably have modifications at some point to boost the Euro rating, whether it was boosted enough is another matter.