[Snax]

Looking at the rear of my i3, you can see a legitimate effort at an OEM diffuser. The tray extends all the way up to the rear axle and is preceded by relatively smooth body work ahead of it.

I'd hesitate to say that down force of any significance is created or intended by it, but the extra hole mine has for the gas generator cooling has a 0.01 hit on the drag coefficient of the car. Pure battery i3s don't have that hole.