the hush system is designed to be a straight through system, with very minimal restriction. borla mufflers, espcially the newer ones are designed and known for their free flowing characteristics. this isn't a chambered muffler by any means.
its hard to see the internals but you can see how its straight on the inside with serated piping exposed to the packing versus a cambered system. where it splits into two is a collector type split not a wall like you would find in a chambered muffler.
the restriction of note you might find is on the end of the exhaust where it mates to the downpipe.
its designed to mate up to the factory donut gasket. luckily this peice is put on with a slip joint. it would be easy to take it to a muffler shop and have them weld on a 2 bolt 3 inch flange if it would make it easier to mate to your downpipe.
however, its probably not necessary. some people say that 3inch untapered is the way to go. but honestly, unless you're cranking out some serious numbers, most street cars won't have a noticable difference with this minor restriction in the way.