the exhaust from the manifold comes out in three stages till the silencer....in between the first and second stage is a metallic ring whose job is to prevent the joint of two stages rubbing with each other once the pipe is really hot and expands to a certain extent...that ring wasnt doing its job and when u wud push the car really really hard, the exhaust wud get hot and expand and the ends of two segments wud rub with each other and do khicch khicch loud sound. i got the ring replaced, case closed
