Burning smell in Cabin

Just bought a used 03 Mazda6 v6 engine, and noticed a burning almost plastic/ exhaust smell. Took it took the dealer and they said that it was probably from a leek from the oil pan which they said they replaced. Of course the problem still happens. It is really noticeable after prolonged highway driving and then coming to a stop at a light. Any suggestions would be greatly appreciated. thanks marc.

Take it to an independent shop. A burning smell is often a sign of a sticky brake caliper, and if so this will need to be addressed.