Hurray for me! I got the parts and finally found the time to take care of this problem. I spent the better part of the weekend replacing the throttle body adapter. I wasn't in a rush, it seemed intimidating at first, but turned out not to be, probably because I had all the right tools.
One thing for anyone who might have to do this in the future: the manual says you'll pull the throttle body out through the right side of the bike. My arse! There's no way in hell, don't even try. The fuel rail is in the way and it's just too tight. I pulled it out through the back though, only had to unhook the thick wiring harness from the rail to make some extra room. Easy peasy.
The old throttle body adapter looked real rotten out and was cracked where the top cap met the cylinder. Funny thing is, my high idle issue probably had to do with the idle screw adjustment, which I didn't realize these bikes had until I got to working on it. Now Purs like a kitten at 1000 rpms at idle and I'm a happy camper!
Hot dang this thing pulls hard without any vacuum leaks! WOOOOOT!