While this may not be what you want to hear, the best thing you can do is to relax and enjoy your summer. Anything you learn this summer will be long forgotten by boards time next year, and you run the risk of burning out during ms2 and not getting as much out of it as you should.
If you feel like you must do something, I'd suggest Firecracker and start banking cards that cover your m1 material and try to keep up as best you can as ms2 gets rolling. The thought here is that their spaced repetition algorithm will keep you reviewing the material during the year and thus make you less likely to forget it over time. Any isolated study at this point would be about as useful as prestudying for ms1 would have been.
Pay no attention to your World scores at this point because the questions and answer choices, even for m1 material, presuppose ms2 knowledge. The vignette for a physio question may well contain pathology or pharm concepts even though the actual question tests a physio concept.
For example: (just making this up)
A 54 year old man presents to the emergency department complaining of sporadic syncopal episodes. Vitals at presentation were BP 135/83 Pulse 88 RR 19 T 37.4. Physical exam was remarkable for a ii/vi systolic ejection murmur best heard at the lower left sternal border that grew louder on inspiration. Transthoracic echocardiography revealed a pedunculated mass in the left atrium. Studies performed during a syncopal episode would most likely demonstrate which of the following?
a) increased ejection fraction
b) decreased ejection fraction
c) increased pulmonary capillary wedge pressure
d) decreased peripheral vascular resistance
e) Decreased right ventricular pressure
f) Increased left ventricular peak systolic pressure
This is a basic physiology question, but does presuppose that you recognize a myxoma and know that the pathophysiology of the incidents in question derive from the tumor intermittently obstructing the mitral valve - decidedly 2nd year concepts. Once you know that the mitral valve is obstructed, it's obviously C because mitral pressures will increase just like they would in any other obstructive mitral lesion which would be reflected in your PCWP. A year from now you'll consider this an easy question, but right now has a couple elements that would make it unfair to ask you unless I said "...pedunculated mass in the left atrium sporadically obstructing the mitral outlet" at which point it would be fair game.
[distractors: a&b are wrong because EF wouldn't change; you'd just have less EDV; d is wrong because your body would increase resistance to shunt blood to vital organs during hypotensive episodes; e is wrong because RV pressures would increase due to backing up from the mv obstruction; LV systolic pressures would decrease due to massively decreased preload]
So, save World for next year sometime when you can truly benefit from it and enjoy your summer!