The current exhaust is designed to aid cylinder filling/scavenging. You'd have to do a dyno run with the seperated dual exhaust to see if it was a good thing or bad thing. My WAG is that you would loose midrange torque 5-15 ft lbs) but gain top end HP. (3-5hp). Honda designed the system for a reason. If you look at every aftermarket full system and race system, they all follow the same design. It would take some serious R&D work on your part to come up with something better. Think of all the hours that race teams and Honda put into the stock exhaust. Simply going with 2 seperate pipes would have been done already if there were advantages..