Really? Now I'm confused as to which one to buy but at the same time things are starting to make sense.
For example if you read the ar design description "The only TRUE 3" catless downpipes currently on the market! 3" tubing until cat-back flange - all systems currently on the market reduce to 2.5" much closer to the turbocharger." it appears the point they are making is that they are 3" for more of the length than others, but they still taper to 2.5". In that case does anyone have an idea of how the various types compare, which stay at 3" the most?
http://www.ardesign.info/store/bmw/b...downpipes.html