You pretty much want to match your exhaust tubing size to your header collector. I'm a firm believer in running 2.5" all the way back. Another thing to remember is you'll lose size on the bends if their not mandrel bends too, so upsizing a quarter inch from your collector might not be a bad idea either. I'm thinking of buying a wad of mandrel bent elbows from summit, cutting and welding them to get my bends and axle arch, plus I kinda wanna run stainless all the way so I never hafta worry about it again. I think my friend will let me use his tig welder to do it, which means I might actually hafta learn how to tig some day.
