Hi, I'm a new guy needing alittle help, actually lot of help. First off I'm new to this computer thing & the internet. Haven't quite figured out these dissutions&chats also. anyway back to questions. When you add a 16cm housing do you need to order it with what ever size exhaust system your going to use or are they all the same as far as matching to the down pipe size or is the down pipe reduced to fit the housing. An inquireing mind wants to konw. Thanks. Just bought a 93 ext cab dually stock auto, 3. 54 diff. from calif. it now resides in Queen Creek,Ariz hot here.