You must get a letter of no objection from the Western India Automobile Association. The WIAA will need to contact your Carnet issuer to essentially verify that your Carnet is good... (Isn't that the point of Carnet?). It's a bit of a pain but you can also sort out your mandatory vehicle insurance at the same time. We e-mailed our Carnet issuer and had them e-mail the WIAA before we made the train trip into town to save us a trip. Vincent Machado was the gentleman we dealt with when we were there last November. You will need photocopies of certain pages of your Carnet and your passport, but there is a handy copy shop on the ground floor of the building.
The contact info is:
Lalji Naranji Memorial Building, 76 Veer Nariman Road,
Churchgate, Mumbai - 400 020, INDIA
Tel.: 022 - 22041085 / 22041271
Fax: 022 - 22041382
If you take the commuter train to the Churchgate station, the WIAA office is located less than two blocks away from the station.
For more info, you can read about our experiences in our trip report beginning here http://www.horizonsunlimited.com/hub...0-6#post359409
Good Luck and have plenty of patience!