The issue is with the Silencer Bolt, Sorry as I'm not an auto expert. Last time, my SE allowed me to see the bottom of the car and I suspected it. But they were sure that the issue was with the Silencer. The noise started when the ODO meter reading was around 750KM, now its 8300KM. In between we got it checked by Service master. It was also my fault that when ever it repeated, I failed to take it to them as it was 35 kms away from my home.
Noise start when the engine is hot, ie silencer is hot. Its like a rattling sound. Once it starts, we can simply recreate it by applying throttle, making car on with Hand brake. Last time we identified that it can be recreated when we shake the silencer. I don't feel like blaming Service masters, but.. From the day when I payed for my Waggi, started the night mare. The purchase procedure was a head ache for me. If TAI allows, I can share it. Also the paint on Bonet cover is like melted. When I went to the service guys, told that its because of Crow's **** (donno the exact word) which made the paint to melt. Maruthi seems to start treating crows, not improving their build quality. Still I love my Waggy. Let me try posting the noise. Also Service masters has given appointment today. I may take Waggi there.