Originally Posted by jdubhack
Stock is 2.5". Most aftermarket (FSWerks, Borla, Magnaflow) are offering 3". They just missed the boat.
Just because that is the most requested size, and therefore very popular, does not mean it is the best performing. Most aftermarket stuff for late models isn't about improving performance as much as aesthetics.
When a shop does good R&D for improved performance, you get people that want something different because they think will perform better, despite the testing and development done.
When I was hotrodding my first BBC, I went through four different cams until I finally listened. Then I got the tiny little cam Alan recommended that wasn't very "high performance" in my mind and went the fastest. Probably should have just taken the advice of the guy that builds BBC race motors and owns a dyno.