I would prefer to run a single pipe set up to keep things simple and lighter.
The Z3 2.8 Magnaflow set up is a single pipe system with dual tips. This is the back half section, there is also a catted front section that bolts to stock manifolds (or shorty headers). If I'm very lucky I can just add a little section between the front and back half and be done.
http://shop.bimmerbum.com/products/3...-exhaust-16712