
That GS will take off pretty damn quickly; fast enough to both wheelie and leave you doing the superman.
But, if you must have more power...The only economical way to do that (without getting a new bike) is do an exhaust and jet kit, and get a smaller front sprocket. Everything else (turbo, bore job, etc) is way expensive for what you get out of it.
And "freedom of choice" is a lame excuse when other people's lives are at stake. If he wanted more power for riding around on deserted roads and whatnot, that's fine. But if he loses control of that bike (which even on a GS500 is very easy to do) he could injure or kill someone.
And that message HAS to be 'like a broken record'; 'cause if it isn't, many won't get it into their heads.