I'm a little curious about your method. I get that you can go through the stand-alone's quickly. But for passages, how do you fly through them, aren't there times where you don't understand the set up or the information you need is inside of the passage to answer the question? Everytime I'm in a passage, I feel like I have to go back and look at/read the passage to make sure I a) understand the scenario correctly and b) make sure that there's no component from the passage that needs to be integrated in answering the question. How do you combat/deal with those scenarios?
I know you're not talking to me, but...
a) I read the questions first on the science sections. Usually you'll have at least 1 or 2 "discrete" questions per passage. Answer these right away.
Then go through and read the passage. By now, you'll have read the questions and know the "buzz words" the AAMC is looking for. Once you see these words you'll naturally start paying more attention.
b) Once you have your answer, know why it's right. What I did for my MCAT last Friday was to go through choices ABCD for every question. If A is wrong, cross it out. If B is wrong, cross it out. If C is correct, then select it and move on without even looking at D. Only 1 answer can be correct. This will save you time. Just make sure you're reading the question and the choices carefully.
Don't spend time on the question if you don't know the answer, or can't deduce
how to do it within 10 seconds. This is why you study. Put your best guess on and move forward. Usually these are the ones you'll get wrong anyways.
My PS practices I was finishing right on time. Usually with 1 or 2 minutes to go. For test day, I finished with 5 minutes to go. You will never know until you take the test.
As long as you're content with your scores, you'll be fine. A 12 is a 12 whether you finish with 20 minutes to go or 20 seconds.