it is a test pipe. that's what it is used for. testing exhaust setups without the flow restriction of a cat. works great for when you run an auto-cross and have to pass emissions at the end. if you can get your test pipe off and the high flow cat in before emissions, you'll be fine, and you'll have had some extra horsies to carry you around the track.
I've got the SSA headers with the ARK N2 exhaust...straight pipe, no cats. sounds MEAN! In so-cal, I get away with it. anywhere else that valued peace and quiet...I'd get pulled over in a heart beat