I have Pulsar 180 UG4 since nearly 2 years. I have a doubt that Bajaj service men have changed the carburetor with an old one as my bike is behaving differently with a different sound. If this sound becomes a habit to me then I will loose my ability to differentiate my bike's original sound. Is the engine number that is engraved on the left side bottom of the engine same as the number that is engraved on the carburetor on the right side. I haven't checked this number initially at the time of purchase. The next time when I buy I will take a picture of its number with the bill so that they have nothing to steal but petrol. Its price is around Rs 2300 at Bajaj shop. When should I change it?

It would be better if a security camera is installed in Bajaj Service Center so that they can record and give us the video clip of our serviced bike at delivery time. When security cameras are present in every shopping mall why not here.
I am happy with Bajaj Anti Piracy Movement in this link
Bajaj