I usually do not mark the passage, however, and just slowly read through it once (usually takes about 2 mins), then spend the rest of the time on Qs. I have come to realize marking generally slows me down and isn't too helpful, as I can usually keep in mind where cause/effect, author's perspective, and all that jazz is.
My RC scores have increased dramatically since I started "over-marking." I used to miss 5-8 questions per section, now I only miss 2-4. I take a lot of notes, focusing on the main idea of each paragraph. I read quickly while I take notes, and I tend to finish my reading within 2 minutes (as you do). With this strategy, I am able to read the entire passage and paraphrase at least the main ideas simply by looking at my notes. I find it to be very helpful, and it doesn't slow me down a bit. In fact, it speeds me up significantly. Once I finish reading I can attack the questions, confident I've already written down most, if not all of the information that will allow me to properly answer each question.
Additionally, I like to do a quick-read of the questions before I start reading the passage. In more than one instance, I've been able to answer a question (usually #3 or #4) before I even finished reading the passage.
Take notes, but only notes that will actually help you!