Hi Sonam02,
Many Business Schools have publicly stated that they do not consider one's IR Score when evaluating an application - so you probably have nothing to worry about with an IR4. If you still want to put some extra time and energy into your IR studies, then you might first think about how you are studying for Verbal CR. Integrated Reasoning prompts and Critical Reasoning questions are based around the same general skills, note-taking and pattern-matching - meaning that if you improve in CR, you will be honing the same skills needed for IR.
Before I can offer you any additional advice for your studies, it would help if you could provide a bit more information on how you've been studying and your goals:
Studies:
1) How long have you studied?
2) What study materials have you used so far?
3) How have you scored on EACH of your CATs (including the Quant and Verbal Scaled Scores for EACH)?
Goals:
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?
7) What Schools are you planning to apply to?
GMAT assassins aren't born, they're made,
Rich