can anyone help me out here im wanting to remove my kat and make my own pipe to replace the kat but need to know the pipe sizes main pipe into kat and pipe sizes coming out of the kat ..my car is a audi a4 cab quattro 2004 .. i dont wanna buy one as there to dear to make plus my mate has a tig welder so shouldnt be a problem to make cheers if you can help me out