IMO, their 4-into-1 collector design is horrible. It would make more sense to have a replaceable collector so a better one could be used, and also have the option to change between 3.0" and 3.5".

I use an old set of Hooker 2" x 32" x 3.5" Super Comps and hang long collector extensions off 'em. I figure the dyno results are more applicable to what engines like mine will see in a street car with a header that can be used in a full-body car.

If you loose 20 HP between "ideal" dyno headers and headers the car actually uses, that's 20 HP you're never going to see in the real world anyway. Might as well make the dyno data reflect the intended application as much as possible...