it is also know as a carb bellmouth, it allows more air into the carb (as well as lots of dust, bugs and even small birds).
It is unlikey to make any difference to a bog standard 500, although there is the possibility it could cause the engine to overheat or in the most extreme case you could hole a piston.
If it is made from spun aluminium and comes will all the the jets needed and instructions on setting the carb up i would say it would be worth it.
But if you fitted this and changed the carb settings the car would no longer be bog stock
