Are you sure your carb is getting full throttle travel? The carb's throttle arm may only be traveling 3/4 of the way instead of bottoming out at the stop peg. This is especially a likely scenario if you have changed carbs without bending the accelerator linkage arm to match. I posted about this problem the other day in a thread about Zenith carbs. Did you see it? Here it is:
https://www.fordbarn.com/forum/showt...33#post1493833
Marshall