[Scott]

Yes, a lightweight aftermarket single exhaust would significantly lower weight.

The stock, all-steel exhaust system weighs close to 80 pounds if I remember correctly. Some of the lighter single exhausts (such as the JIC full-titanium single) weighs in at just under 20 pounds total.

Furthermore, most of the top-end single ehxuasts available will increase horsepower (albeit quite slightly), whereas most aftermarket duals offer little to no performance gain and only moderate weight reductions.

So why hasn't everyone switched to single ehxausts? Well, many for the same reason I didn't. Nearly every single straight ehxaust available for our cars is very loud and harsh sounding. I went with a quality aftermarket dual setup and the sound is very moderate and isn't raspy at all.

As for why Honda built the car that way, it's mostly just for looks. Dual exhaust is often one of the trademarks of a sports car.