It seems Sportec is (soon?) releasing a dual exhaust with electric flap for the M135i !
With downpipes, it would add 8 HP.
http://translate.google.com/translat...i.html&act=url
http://www.sportec-tuning.de/bmw/1er...anlagen-135im/
Added to list.
I'm still waiting for someone to release a quad exhaust !