Thin oval section tailpipes of modern blown exhausts are good for aerodynamics but probably are bad for engine performance. Ferrari uses this "expansion chamber" to add volume to their engine's eshaust tailpipe (altering pulse rates at the same time), trying to regain all the lost performace due to the blown exhaust concept.
The oval exhaust would not have to be bad for engine performance.
I have seen these expansion branches in studies or models, but never in on actual race car of any type.
The exhaust collector pictured above fits under existing body work?