Is there a chance that this might be a carb tuning issue when the primary circuit transitions in?
I recently asked a local parts store why the newer lower hoses did not come with a wire. They said that the manufacturers are using better rubber materials that no longer require the wire insert which prevents collapse. How old is your lower hose?
1970 YO7 A66 [Canadian Export] F8 Challenger 340 (Currently in shop for stroker assy.)