The cars certified fuel mileage on the base car is without the gurney flap.
The CFTP car certified fuel mileage is with the wing in the “street” setting.
The base GT500 will get significantly worse fuel mileage with the gurney flap installed.
They only put that in the manual for legal reasons.
And another CFTP wrecked.
Wing and seats gone..............maybe more.
https://www.copart.com/lot/32542851/2020-ford-mustang-shelby-gt500-nj-somerville