Just starting second year and thinking about going into a competitive specialty. So far, I have a summer project resulting in a first author pub in this specialty and several coauthors on pubs during first year in research unrelated to this specialty. Should I try to connect with a PI in this specific specialty during second year and try to pump out another pub or would my time be better used for studying and concentrating on step1?
There may be exceptions, but it's probably unlikely you'll be able to get into a competitive specialty without a good to great Step 1 score. If doing more research is going to impede you from getting a good to great Step 1 score, then I'd say forget the research and focus on Step 1 (especially since you've already done a lot of research).
However, if you're applying to a field like rad onc where lots of people have a lot of good research, sometimes get LORs from PIs who are in a position to help them get an interview, etc., then this is something else to factor into the equation.
There are also other questions like how you've been doing in med school (if you're at the top of your class then you may not need as much time to study for Step 1 and can possibly devote more to research), what the quality of your research is like so far (although to be fair as a med student almost any research likely looks pretty good), what research the PI in this specific specialty wants you to do (if it's worth doing), whether you'd be happy in any program in your competitive specialty or if you're also aiming for the very top tier in your competitive specialty (which may an indication for how hard you have to work to get there), etc. You don't need to reveal anything you don't want, but more details might help people better help you.