Anyone know why the Volvo 8.1 Gi engine (375 php) would have a max RPM of 4600 compared to the 8.1 GXi (420 php) of 5000? With the same gear ratio, wouldn't the GXi perform a lot better? As a comparison, the same 8.1 liter engine in the Mercruiser 496 (375 php) and 496 HO (425 php) don't have...