I was fixing to ask if this was possible. The proof is right there. Well, when I was in Louisiana, there was a small bike shop that swore a good 4in1 gained 20 more hp proven with dyno runs. When I was heavy into large radio control helicopters, I made my own headers out of 3/4 inch copper tubing as it was cheap and easy to work with, and easy to weld. I tried over and over adding or taking just millimeters off or on the length until I got max power. Now not only the header but the shape and size of the muffler chamber made a big difference too. A muffler with a progressively smaller point at the end with the exhaust exiting about an inch or so from the end, was a killer combo. You could easily get 200hp from that setup on that bike, good tune, well-designed exhaust system, and evidently the better gen2 clutch for some reason and with a good lightweight rider. The long story kept long, yeah it's possible with the right header muffler combo, tune, etc!
