yea this sounds like the plates are worn. I know my steels had been blued from all the slipping on my old bike. It felt like something on the road but it was far from it. You can always take it out and inspect it... not sure if you can loosen the clutch on the busa since its hydraulic? i used to just loosen it on my old bikes till i ran out of adjustment, then replaced lol.
oh yea, if you got 49k from a stock clutch, get a stock clutch again. No need for anything else if the bike is stock!