I do agree with the above posts, your performance on your third year rotations, in particular, your EM rotations is very important. While strong board scores will no doubt help you, I don't think it is as heavily weighted as other fields such as radiology or ortho. I have heard that some EM programs have a hard cutoff for scores, but I think they are far and few inbetween. While research is nice, I do agree it is more of icing on the cake. Unless you did ground-breaking research, it won't make up for other more important areas. I feel the following are key to a strong application:
Clerkship grade (esp EM)
Boards
EM LOR
While EM-related activities are nice, from my own exp (I had none), I don't think it affected how many interviews I got. Good-luck!