I don't know much about the Yale program, but there's a couple of Yalies MSTPers on the forum so they can answer questions regarding their program.
First of all, I'm a stickler for semantics so I'll grind on this...you never TRY out an MD/PhD program. These programs are designed for a specific purpose, to produce physician-scientist; physicians who are trained in both basic and clinical science in a pursuit to integrate both fields.
If your only goal is to be an emergency physician, then an MD/PhD would be a huge waste of time for you. Having the extra degree would not be of much benefit to your practice. If you want to teach at a university later in your career, you can do it with just an MD. At my undergrad, Univ of Texas, there are many MDs who conduct basic science research as well as lecture in undergraduate and graduate level classes.
Have you spent time doing research in a lab? If you haven't, I suggest you look into summer research programs or research opportunities on campus. If you enjoy what you do there, maybe the MD/PhD route is the way to go.
Hope this helps in your endevors.