Can you tell us what kind of practice tests you've been taking? (e.g. Princeton Review
, Powerprep) Kaplan
tests are generally harder than other practice tests.
My instinct tells me that you probably need to study more. I'm assuming that you scored higher in the verbal?
I would concentrate more on geometry than permutation/combination. In my own experience (as a high-600 scorer), I've gotten one or two permutation/combination problems on the actual exams. Those weren't too difficult either.