Confused with piping for TD's
 

I want to come off a set of 1 3/4" LTs' cats, x pipe, muffler, out the back... And from what I've read 2.5" piping is what most people are using, and I'm going over the axle so 3" would be too hard to fit... Before I go ordering the wrong hardware I want to make sure I'm not missing the obvious somewhere...

Should I run 2.5" right after the headers, or do people down size as they move back?

Should I get a X-pipe 2.5" on all 4 ends? (Part #10791)

Looking to us Magnaflows for the muffler... Either the Race Style or the 4X9's. The Inlet/outlet are either 3.5" or 4"... So do I use bigger pipe here, do I need to order a muffler with a 2.5" Inlet/outlet?

any help on the pipe sizing stuff?

TTT
Anyone?