What are my chances of getting a call from the tier 1 MBA institutes like IIMs, FMS, XLRI, SPjain, etc., if I have a 3 year drop after my graduation?

If your academic performance was fine and your score is a bit on the lower side, you can get Tier-1 institutes like IIM, FMS, XLRI after fulfilling some requirements. It would be a bit difficult to compete with the fresh graduates but it is still possible.

A gap of 3 years and no work experience after graduation is a negative point that can be easily pointed out in your CV. You should be honest with your reasons and make sure to avoid unnecessary mistakes, you can walk through it in your interviews and can get enrollment in these top MBA Institutes.

A good suggestion for you would be to deeply do a quick review of what you had learned from your experience with engineering job preparations. You should consider the reasons that have made you shift towards pursuing an MBA course.

If you can back all this up with a decent CAT/XAT percentile score (around 99.5 plus in your case), you can get a call from these institutions.