Hi pavag,
The scoring algorithm on the Official GMAT is far more complicated than most people realize. Since that algorithm is proprietary, no GMAT company has an exact match for it, thus CAT scores can vary a bit based on the 'biases' involved in their respective designs.
Keep in mind that a CAT result is also only as realistic as YOU make the CAT-taking experience. Thus, YOU have to take the CAT in a realistic and test-like fashion, including taking the ENTIRE CAT (with the Essay and IR sections), at the same time of day as your Official GMAT, away from your home, in a test-like environment and NOT do anything unrealistic (pausing the CAT, listening to music, skipping sections, etc.).
Before I can offer you the specific advice that you're looking for, it would help if you could provide a bit more information on how you've been studying and your goals:
1) How long have you studied?
2) What materials have you used?
3) How have you scored on each of your CATs (including the Quant and Verbal Scaled Scores)?
4) What is your goal score?
5) When are you planning to take the GMAT?
6) When are you planning to apply to Business School?
GMAT assassins aren't born, they're made,
Rich