An ammonia smell and nothing has been changed?
I remember reading an article on this awhile back but couldn't find it; I did, however, find this one
that also discusses the ammonia smell from car exhausts .
It also seems certain SUVs (often V8s) experience the same thing in the USA. As I've never heard about this before, I wonder if the remap has changed the gas out put from the engine and therefore is forcing your catalytic converter to create the smell while processing the exhaust?