Take one of each of Kaplan's and M-GMAT's.

Or else reset the GMATprep exams and take it one more time, and use one of Kaplan or MGMAT.

When you reset the GMAT prep you're likely to see at least some of the same problems, so if you get one you know the answer to, just put in the right answer so that you'll see some different problems.

Remember: your goal in taking a CAT shouldn't be to "predict" how you're doing exactly. Focus on your process, not the score. How was your timing? Did you make silly mistakes that show a lack of focus? Things like that.