Guys after noticing that my Ignition coil was giving orange spark, I opted for replacing the coil after ensuring that all other components of ignition system were fine.
I went for GT Denso Coil (Purchased for Rs. 2600).
After replacing, there is significant reduction in engine vibration and noise. Much improved performance under load. And something strange but true that there is no smell of oil burning from exhaust and no smell of unburnt fuel. Also my oil level getting dropped has stopped ( I will confirm this again after sometime to ensure that my observation is correct).
Spark is now bright blue. But there is terminal on coil mentioned "B", it is unconnected, anybody has idea about this "B" terminal on coil? No such terminal "B" was on older faulty coil.