You posted a week ago that you're taking the test in a week, so I'm aware that we've probably missed the window for advising you, but I wanted to respond in case others find themselves in a similar situation.

It will be extraordinarily difficult to improve from 35 to 48 in a week. I can't recall a specific instance in which a student of mine has achieved that, and I've been doing this for almost 15 years. I'm willing to bet that this is why nobody has responded to your post before now. Nobody wanted to be the one to tell you that this would be very unlikely to happen.

For others placing similar expectations on themselves, this isn't the kind of test on which you can cram. It's not just a matter of learning some stuff and then anybody can score in the 99th percentile (which is the percentile for V48); this is a MUCH more complex situation.

A couple of general things:
- You can't gauge your performance simply on percentage correct. Difficulty level and timing are major factors in the scoring algorithm as well, so just focusing on your "hit rate" doesn't tell you (or us) much.
- If your performance is fluctuating a lot within a particular type of problem, that's typically an indication that you have certain serious strengths and certain serious weaknesses. When you happen to get more stuff aligned with your strengths, you do better and when you happen to get more stuff aligned with your weaknesses, you do worse. So you need to go figure out what those strengths and weaknesses are, and then attack the weaknesses.
- The fluctation could also have to do with your timing throughout a section - so you need to check that as well. You might be fine within a particular question type but your percentage dropped because you spend too much time on questions of some other type, and then you had to rush and made mistakes on problems that you'd normally get right.

Hope you did well - if you don't mind sharing, let us know how things went.