I could cut the end of the header (or the end of the pipe) slightly shorter, as the Novarossi pipe is slightly longer than the stock pipe that came with the car, and they are attached with a silicone tube instead of springs and a gasket. But how would I know how much to cut off? It seems like I would need to know both the exact max RPM of the engine as well as the exact exhaust velocity in order to shorten the exhaust by the right amount.