Tima is absolutely right about passages exposing your strengths and weaknesses within the material. They can also expose your strength and weaknesses in terms of testing skills.
Many of the questions in the BR science books have questions that are intentionally ambiguous (questions that could be interpreted multiple ways) where you need to consult the answer choices to know what the question wants. If you are missing these types, don't worry so much, because the answer explanations address test taking strategies (usually POE). The design of the books is such that you are meant to learn strategies and techniques from the answer explanations. It's a basic philosophy of the BR books, which is why the answer explanations in BR materials are so much longer than ones in other materials. You learn best from reviewing questions you get wrong.
If you're missing 2-3 questions per passage on average, that's right where you're suppose to be if your goal is a 10-11 on that section. I know it's really hard to not pay attention to the scores, but try to not put so much credence in them. It's about learning and reviewing at this point, and scores don't matter yet.