The car rules under an FM2 are different from an FM3.  The only type of FM2 that allows you to have a foreign-plated vehicle is called Inmigrante - Rentista.

Rentista means a person who lives on his own funds. It does not mean renter although it looks like it might.  There are several other classes of FM2; none will allow you to have or even drive a foreign-plated car.

This restriction does not apply to an FM3.