Similar to OMG (Oh My God), a difference in semantics (or typo), makes AMG similar to Ah My God, or Ah Mah Gah.

Mercedes-Benz's small performance division. Takes regular Mercedes's, adds new wheels, a really powerful handbuild and assembled engine, and probably a new air dam and exhaust tips.

AMG is the acronym for Asian Muscle Girls
An Asian Muscle Girl is a strong, muscular, and/or buff Asian woman.

The letters AMG stands for Amazing motherfucking G-ride

History
This acronym was created November 17, 2012 during a heated discussion in Malmö between two Babbar residents in Lund.

sources:
the truth

A class of the car Mercedes Benz.

All Music Guide. A Web site that has a lot of information on music and is contributed to by the public. MTV.com gets its information from All Music Guide.