I am sure that you know already that EM is very competitive right now. With that in mind, you will want those USMLE scores as high as possible... while I know of people who matched EM a couple of years ago with Step 1 scores in the 210 range, I would not try to bank on that happening in the current environment. A 220-230 probably is a minimum to get an interview most places, from what I have been reading. Research probably isn't going to hurt, either, and don't forget that special EM LOR.
However, the strongest advice I can think of is to apply broadly, whatever you do, and you REALLY need to start thinking beyond the freaking East Coast. Come on now... it's 3 (or 4) years for residency, and after that you can go wherever the hell you want. If the only place you can get a residency is in a so-called "flyover state," are you honestly going to risk not matching into the specialty for which you are professing your love simply because you didn't want to live in Oklahoma (or wherever) for X amount of years? Because that is what you are essentially saying, here. "I really-really love EM... but only if I can get it on the East Coast or someplace close." Frankly, in the current match situation -- and with EM especially -- that mindset ain't likely to cut the mustard. (My buddy just graduated his EM residency in Oklahoma, and is moving this week to his home state. Somehow, he and his wife made it through living there, even though it wasn't where they wanted to settle down, and now he's got his dream job in his dream location. I'd go ahead and ask him if he thought it was all worth it... but IMHO that would be a rather silly question at this point.)
Would you be happier in FM (or IM, or Peds, or whatever the hell else) than EM, just because it allowed you to stay on the East Coast for a couple of years? That's the question, here. The match is already not on our side as FMGs, and it's getting tougher... so if we want a specific specialty, we had better be ready to sacrifice for it.
Just my .02. Good luck!
"When I haven't any blue... I use red."