I'm going to work for Kaplan, so maybe I shouldn't say this, but: Kaplan practice tests are not a 100% facsimile of the real thing. Kaplan slightly de-emphasizes factual knowledge on the science portions, IMO, when in reality factual knowledge is all that matters on the discrete, non-passage questions, and factual knowledge is critical on many of the passage questions as well. They start off in the big book by decrying the belief that "The MCAT is a test of science knowledge" as a myth when in fact, hard knowledge is fundamental to doing well in 2 of the 3 main sections. Reasoning is king only on the verbal section. If you're better with factual knowledge, Kaplan exams will understate your score.
I highly recommend the "real" practice exams from the official AAMC MCAT site. Yes, they are ridiculously expensive but well worth the price. I did the deal for 3 exams for $80. That plus the freebie meant 4 exams. I used #3 as a pre-test, #4 to help hone my review strategies, #5 a couple weeks before and #6 as a dry-run a couple days before the real thing. Look up all your missed answers from your books, and for the science sections identify which were the result of faulty reasoning and which were the result from not knowing the material.
FWIW, I bombed my first two practice exams, scoring ~24 on each. Then I just decided, hey, screw being intimidated by this thing. I'm going to see it as an opportunity... a way to show the admissions committees just how much I should be a doctor. The Kaplan approach is right on this key point: An aggressive attitude toward the test is the most important thing you need to beat it. Confidence is 90% of how well you do. Sort of like on a first date
I know so many people who get nothing but A's on classroom exams, but bomb standardized tests such as the SAT, MCAT or LSAT. The only reason is that they let themselves get intimidated.