I started smelling ammonia when a drive. What can be the reason?
I did recently changed the exhaust pipe. I drive infinity G35.
Have you changed the cabin filters lately?
Black mold can smell like Urine-Ammonia, this mold can also grow on the ac evaporator coil.
Pull the cabin filters and check for mold.
Other than this it could be a rich running engine that causes the catalytic converter to put out strong odors.