Why are you missing the 600-700 level Qs? It may be that you happen to be better at things that are usually harder for the general population, and worse at things that are usually easier for the general population. (Difficulty levels are based on the whole population, obviously!) You'll need to work on whatever those weaknesses are.
Or are you making lots of careless mistakes? When you look at these questions afterwards, do you think, "Oh, I can't believe I did that / picked that? What was I thinking / how did I make that mistake?"
If so, then that's a completely different issue - you do know how to do these, but you're making mistakes and so you need to figure out how to minimize these mistakes. Read this:
http://www.manhattangmat.com/blog/index ... -the-gmat/Finally, you say that your test is in 1 week. How does your overall scoring level compare to what you want to get on the real test? If you're scoring at the level that you want, then it doesn't really matter - you're fine. If you're NOT scoring at the level that you want, then it's unlikely that you'll fix whatever the problems are in 1 week, and so you should consider postponing your test.
If the issue is more one of careless errors (you're capable of getting a higher score already if you could just minimize the errors), then you may only need a couple of weeks. If the errors are being driven by a bigger problem (eg, time management), then you may need 3 or 4 weeks (or longer, depending on the size of the problem). If you've got fundamental content issues and you're still decently far from your goal score, then you're likely looking at 4+ weeks.
So back to my original question: why do you think you're missing these questions? And how do your practice scores compare to your goal? (*Note: did you take those tests under 100% official conditions? If you gave yourself ANY artificial advantages, such as skipping essay and/or IR, taking longer breaks than allowed, etc, then your practice scores might be inflated.)