With the Tony, because of the tight cowl, I was getting vapor lock in the carb causing all kind of problems, engine out, lean running etc. because of the carb setting right above the muffler can of the pitts muffler. Finally put in the "blast tubes" ducting cooling air to just above the carb and the cowl flap to help remove the cooling air. Seems to work as I have had no problems since.

On the P-40 I also ducted air back to the carb. This was easier because of the top scoop. Notice I opened up the cowl flaps. Not sure if all this was necessary on the P-40, but certainly didn't hurt.