How about the stock exhaust system for Gen1 (fuel consumption etc.) Does the full exhaust modification with the headers realy gains 10hp?
Most aftermarket full exhausts with header and muffler(s) will give you around 10 more hp at the wheel, if the bike is properly tuned on a dynomometer(or has a base fuel map from Power Commander, ECU Editor, or similiar ecu tuning unit) Some are more, some are less, but it's an average to expect. It's also a noticeable improvement on idle and throttle response. It's nice to have the catalytic converter gone on 08 and newer Busa's too. Depending how easy you ride the bike you could see a small loss or gain in gas mileage, it's not a very significant change.