I think those venturi inserts are of a help when you have a short track and too powerful an engine. They just reduce max airflow to make the vehicle more driveable (less power). For bashing, I'd remove it. You may have to re-tune a bit, but in theory you sholdn't have to, as the mixture sholdn't change. Less air coming in, makes it draw less fuel from the venturi and the mixture "should" stay the same.

hmmmm........I don't have much experience with these inserts....anyone else?