Quiet Quad Exhaust??
Has anyone had an exhaust/muffler shop custom weld a secondary pipe to the stock 135i muffler to make a quad exhaust?
I'd like to do this but wanted to see if anyones done it before to get their thoughts on it.
I'm trying to keep the volume/sound as close to stock as possible
Another reason is $$$, shipping an actual quad would cost as much as the exhaust itself