Borla S type question

[BBR]

What is the coupe? Does that come with the resonator?

That was autocorrect typo.
Coupe = xpipe (upper RH of borla diagram)
That kit does not have the resonator.

 

[parker3]

That was autocorrect typo.
Coupe = xpipe (upper RH of borla diagram)
That kit does not have the resonator.

what exactly does the resonator do? Is it necessary to have? When people get the Borla s type do they usually add the resonator? Is there a big sound difference with and without it?