Sounds like either a vacuum leak or the throttle isn't closing. Last carb I had was a '72 Datsun & I've never done Hondas or Chevys, so I can just make vague generalizations.

Is the throttle closing all the way? How about the secondary? Is the primary-to-secondary linkage goofed up so the secondary is open a little at idle? If it's closed, I'd keep looking for vacuum leaks.

What's the third barrel? Only 3-bbl I've ever heard of was on my dad's CVCC Civic, & the 3rd was really tiny. Is that what yours is?