I had a similar problem but I found a few tips that worked for me. I'll number them below.
1. Speed reading
On YouTube there's a Tim Ferris video called How to speed read, I watched that and did what he says (it takes 15-20 minutes) and helped me increase my reading speed so I can skim the text faster and save time.
2. Read the question first
If it's a reading comprehension question and there are 3 or more paragraphs, I have a VERY brief skim of the text and I always skip the last paragraph, that way if there's anything in the question I don't remember seeing, it's likely to be in the last one.
3. Eliminate the east to prove right/wrong answer options
For me, if there's an answer with a date in it, I find it easy to spot in the text and then I can quickly decide whether that's a possible answer or not. More often than not I either find the correct answer during the elimination, or I eliminate 3 which means it HAS to be the 4th answer option - if you're short of time then eliminate 1 or 2 and then guess.
4. Don't bother skimming the short texts, waste of time.
The short passages aren't worth reading, skip to the question and search for the answer instead as you'll save time doing this. Also by the time you reach question 3 or 4 on a passage, you've probably got a good idea of the whole text by now.
5. When doing a question set, if you struggle on Q1 then flag, skip and go answer the rest, but keep question 1 in mind so if you come across the answer in the next few questions quickly press ALT-P and amend your answer.
Something to note, the same tactics don't work for everyone, so trial each one and see which one works for you. I find that if I skim the text and then check the answer, I still have to go and skim the text again anyway so I only do it once.
Hope this helps