Perrin is a downpipe back exhaust. It starts after the S & J pipe like the better known CorkSport exhaust.
Perrin is one of the least restrictive exhaust b/c it is 3 inches, mandrel bent, has zero cats, zero resonator, and has a straight thru muffler.
be aware tho, a free flowing exhaust like that is f'ing loud. I got a $106 noise maker ticket for jus driving by a cop normally which was total bulls***.... but back to the subject.
it's also nice b/c it goes over the rear axel so you'll have no clearence issues.
if you want a full turbo back you can just add a cork sport downpipe which will mate perfectly to a perrin exhaust.