MagFarm, I can now set the idle at what looks like 800 or so on the tach and it holds steady. It does not "hunt" and "surge" like it did before.
When I take off from a complete stop I just release the clutch nice and easy and she rolls out. This blows my mind. With the GL1000 you have to slip the clutch and roll on some throttle in a synchronized effort to get her to roll. It's not hard, but you have to do it right. With the 1500 I just release the clutch nice and easy and away she goes.
I can't explain why the PO set the floats so high. A mm or two could be just sloppy work, but they were both set 3 or 4 mm high.
The lower clamps on the carb intake boots were loose and I can't understand that either, because both were tightened as far as the clamps would allow. There was a spacer around the screw between the two ends of the clamp that limited how tight the clamp could go. On one side the PO had rounded out the phillips head trying to tighten the screw further. The boots seemed soft and pliable, not like they were old and hard. I took out the spacers, replaced the bad screw and tightened 'em up.
I did not replace all the "tubing". It looks to me like the manifolds would have to come off in order to do that. Many of the hoses are formed and curved in special ways. And I cannot resolve the issue of why I have no Shot Air Solenoid Valve even though I have tubing for it and I don't notice any deceleration problems. I replaced the direct manifold-to-manifold tube. I tested every tube I could get my fingers on both ends of and put a clip on anything that needed it.
Good luck sorting out your issues.