I commented this yesterday but I don't think anybody saw it. Porsche totally accidentally (or purposely) included Turbo footage in their original targa reveal. You can clearly see what appears to be the extra vent included on all Turbo models in their teaser video at several points.

911 Targa Turbo Kinda Sorta Maybe Leaked

911 Targa Turbo Kinda Sorta Maybe Leaked

911 Targa Turbo Kinda Sorta Maybe Leaked

No vent of any sort on the normal targa

911 Targa Turbo Kinda Sorta Maybe Leaked

The vent shows up around the 30 second mark of this video