The car in the pic is a guy I know, not mine. To be honest my personal feeling is that it's not something that's a must have from a pure aerodynamics perspective.
The "natural" aerodynamics of the car are v good, as I said these "settle" the car a little better at speed, both the front and the rear we're designed by an F1 designer and are produced by Autostyle Solutions.
But it depends what you intend to do with the car, if your gonna race it then that a whole different situation, if it's a road / track day car then a mere mortal like me will be happy with the esthetics of it.
The 111S already has the diffuser, correct? I was under the impression that the one model that is coming to the states will have the diffuser, but now that I think of it, I have no idea why I'm under that impression. :shrug::
Is the autostyle diffuser any better than the Lotus version? It certainly sticks out more (can't say I'm a fan of that).