At the start of its model life the GS500 had 51hp, at the end it had like 44. Same motor! At the end it gains TPS controlled ignition advance and three jet carbs too - gaining the ability to more precisely meter & control things and it still lost power. I personally feel that at least the model that I owned (2005? 2008? I legit forget) was jetted quite lean. Throttle response was abysmal