[R.G.]

Got it B, thanks for the clarification.

Am I off by thinking that removing the cowl will allow that high pressure air in to the engine bay causing a pressurized area? Having this pressurized engine bay would cause the airflow to hit a wall of air instead of flowing through the radiator and ducts efficiently. Sealing the bottom panel would exacerbate this issue by leaving less area for that air to escape.
Since you have made adjustments in hardware and fueling to offset that but for the average street car would be counterproductive.

The stock cowl seals the center area to keep air out and edges of cowl open to allow hot air to escape. I don't think people realize that running with the cowl off is counterproductive to engine cooling.