The FAQ ruling is that the effect still happens, Yorr gets the stress, but you can still only use Elusiveness/Opportunist only once per trigger (a la Luke Skywalker's ability).
This means that Opportunist + Gunner alongside Yorr gives both attacks +1 die, and Elusiveness can potentially trigger for 4 different attacks in a single round.
I really don't want to get into a discussion. I asked the guys at FFG using the link at the bottom of the page, and I posted their response above. That's the final word. Where in the FAQ are you getting that the effect still happens???
Edited by Parakitor