1982 fb rx7 rats nest is gone (got it that way)
and it doesn't idle but drives fine

 

Somewhere there's a vacuum leak. I'd go through all the ports and ensure they are sealed.

You can use carb cleaner to spray around the carb area to see if the rpm changes.

The other thing could be a bad carb that needs rebuilding, but id check everything else first. Previous owners are a very bad thing in most cases!