[niles]

I think your assumption that boiling fuel is the problem might be suspect.
My experience with air coming directly onto the carb via the scoop results is a realitively cool carb. I have never seen a problem with or without spacers.

I would start an logical elimination process; 1st thing to eliminate is to insure your float hights are correct with engine hot and running. 2nd trace your fuel line route and make sure that anywhere its "sees" the headers, that you have the line insulated and a heat shielded, so that any line (gas or brake) can not get direct radiation heating from the very hot headers

gn