from my experiences so far, it seems like LOTS of places determine whether or not to interview you in IM (which is what I am applying for as well) based on the strength of your Board scores...KICK BUTT on Step 1 and you'll not only have opened yourself multiple doors @ top places in IM, but also in other fields (rad onc, rads, derm, optho, anes.) as well should you decide to switch while you are doing your 3rd year rotations....
Also, try to get some research experience as a 3rd year....doesn't necessarily have to be published (if it is, then that's grrraavvvvvvyyyyy), but atleast get involved in research in your IM department.....
hope that helped