What sled? You can remove the air box, and try moving/wiggling the carbs, looking for cracks in the boot. Other than that, you can use starting fluid spraying the boot area, it will cause the idle to noticably increase.
If you plan to keep this unit, I would just swap them out and to heck with testing them. Carb boots are like $20. I replaced some years back on my wife's new to her-1994 Jag Z. Took me all of ten minutes and some dirty hands. Oh well!
If you plan on keeping it.....replace them with Boyesen Rage Cages and never look back. The bulk of the assembly is aluminum, with only a small portion of it being rubber (connects the Rage Cage to the air box). If that connector should deteriorate, it's easily replaced without removing the whole assembly. And I think, though I'm not certain, that you can replace the reeds without replacing the whole assembly (which I don't think is the case with OEM).