searched..but found nothing

going to have a xs-engineering kit on my 2001 gsr...that is designed around a more or less stock dc2. i have a hks hi power (55mm) which is fine for 7-8 psi...i eventually i am going to get a bigger exhaust once i build the motor and up the boost but i was wondering...would a test pipe benefit me at all? or straight pipe from the downpipe to the muffler be more efficient? i mean its a piece of pipe..i know gains wont be anything out of this world...but itll be less backpressure cause of the deleting of the cat right?