The previous 3D printed ones had the small humps you describe, but after trying with and without, it doesn't do much. They were good to help the porous 3D printed parts with sealing, but on the CF part, there is no problem at all
The inside of the plenum is a regular T shape, with larger radiuses to improve flow.
I didn't use a Y shape for various reason.
I live in the south, on the Riviera
Which video was it ? Because I never went (unfortunately for me ^^) on Anneau du Rhin.
I go back on track in two days ! Hopefully the gopro stays in place more than 5 minutes this time ! ^^