I have a perrin up-pipe, HKS downpipe and a Racing Super Medallion. If you are wondering if it is loud... ...Heck YEAH IT IS!!!! Under 3000rpms, It's not too bad, But beyond that, it is super loud. Not Really inside the car, but outside. The loud noise is kinda strange too. Like a short low note from a Large trumpet, looped over and over really fast. A low note, But not Bassey at all. When the windows are up, the sound doesn't really intrude into the cabin, but when you are next to a wall or another car with the windows open, You Hear it big time. I'm still not sure if I like it.
In addition to this, The HKS downpipe eliminates the stock doughnut gasket after where the last cat was. It is replaced by a standard exhuast gasket with a 3 inch opening. The problem comes in where the begining of the Tanabe has the receiving end of the ball joint, with a loose (free floating) flange. The doughnut gasket cannot be used at all. I am a little concerned that the free floating flange may leak, without the proper doughnut gasket in place. I may have to get it welded. Or try to line it with some blue silicone. I still have yet to confirm a leak, I am just speculating at this point.
I'll let you guys know as soon as I find out.