Tunnel Throat Design

I'm new to aero, so please extend some patience to my ignorance.



I own a Prince LSR P1 car. I am scratching my head on the tunnel design.















The previous owner told me that Pat Prince added the teeth before throat to add turbulence for less downforce. I'm a newb to aero and how diffusers work, so is this correct?



I will be running Hillclimbs and tight tracks like Blackhawk and Autobahn, so I'm more concerned with downforce over drag.