I'll never understand why so many test takers find this important. Can we find the best thread on this question and sticky it in some sort of FAQ?
How does passage length matter? What would you do with the information that the actual passages are shorter, the same length, or longer than question bank x, y, or z? What if someone could definitively tell you that the average length was 91.83 words?
One thing you should have discovered by this point is that passage length does not make the question more or less difficult and it only weakly correlates with time required to answer. My longest question stem, at 10+ lines, was a pharm question about the MOA of a psych drug. You needed NONE of the information in the stem. Conversely, some of the shortest questions are the most difficult because they require more rote memorization (sometimes of material not high yield enough to make it into review books) and less interpretation of tests and pattern recognition.
Probably the most essential "skill" of medical school should be developing your ability to quickly skim a lot of information for salient points (positive and negative) to arrive at a likely diagnosis, some alternates, and deciding on the next diagnostic and therapeutic steps. For test taking purposes, you must decide whether to read the questions and answers first or not. You probably know whether or not this step helps you. If not, test it out on UWorld, an NBME, or Kaplan Qbank. Their stems are all about the same length as the real thing.