im really not worried about running my cat with it
ill have a TBE soon anyway, this is just a temporary way to get a tiny bit more power out of her

 

buschur hardly made any more power on his car going from a 3" catless exhaust to a 3" straight downpipe, and that was with a highly modified evo. i doubt you'll make a noticeable bit of power, especially with the cat. if you want a little power, get a test pipe and run a full exhaust system, it'll probrably make more power then a straight downpipe with a cat on the end of it.