I'd recommend not "ranking" the passage and just do them straight through. If you ask the folks who score 128+ on the CARS, you'll never hear that its something they do. That ranking idea comes from Kaplan and TPR and it's junk. A few questions to look at:
1) Are you running out of time and having to rush on your last few passages? Take a look at the number of questions you miss per passage. Is it pretty steady across or do you go from getting 70% correct on your first three passages to 30% correct on the last two because you're having to rush? Focusing on correct pacing as we talk about on our SDN guide can help correct this.
2) Are there certain types of questions you're getting wrong consistently? It might help to take a look at those types of questions in particular and learn the ins and outs of those.
3) I'd recommend highlighting as little as possible. Highlighting a few keywords per paragraph can help if it helps you get to the main idea of the paragraph/ passage, but if you're highlighting whole senses, that really is offering you no benefit. One tip that has helped many of my students is to wait to highlight anything in a paragraph until you've read the entire paragraph. Then pause, and ask yourself, what was that paragraph about? What was significant and unique about it? What do I want to remember about it. Usually there is a "mini-main idea" in each paragraph that you want to hold onto as you move on to the next paragraph. Make your highlight (include as few words as possible and remember, it's okay two highlight a word or two, skip a few words, and then highlight again.) While you might spend a little more time on each passage reading it, you will likely make up that time as you answer the questions.
Best of luck with your studying and let us know if there's anything we can do to help you!