Say i have 504 EVs on my Vulpix. Since it has PokeRus and a Power Bracer, if i fight a pokemon that gives of 3 Atk EVs it would be 17. That is OVER 510 so do the EVs just get ignored and you could still get 6 more or does the EVs just go in to the 504 to make 510 and the rest of the EVs that would be gained get ignored?
The extra EVs would be ignored, you can't get more that 510, and it wouldn't be fair if you lost all those EVs now would it? But you will get to 510.
Source: See comment; Experience.