[diverdan]

Love my Borla system. Exhaust pipe size is primarily dictated by the displacement of a single cylinder in the engine since only one fires at a time. An additional pipe adds more weight as it's size is dictated by that single cylinder displacement. "Big hat, no cattle," syndrome.

As for the fumes, check the drains and in the spare wheel well and other spots in under the car and behind the rear bumper cover such as old grommets, but I'd bet on the rear hatch seal. (Or may be the tail pipe length?

Diverdan