Yes, it decreases Performance.
It does not decrease Performance. I've had SEVERAL friends with dual exhausts (Y pipe) and they love it. It provides the same Performance as would a regular axel back/cat back system would. I'm going to stick with that untill i see some dyno sheets. The following are examples.
Ok Eyger, I'll grant you that with the "Y pipe" you may not lose Performance, but there is certainly no advantage of that setup over any other aftermarket exhaust
that has bigger piping than stock. It's just for looks, and as such, it's a waste of money
IMO since the whole point of getting an exhaust is Performance (and perhaps the sound, which can also be easily achieved with a single pipe).