i've got to rebuild my exhaust for my HMT turbo setup

is there any advantage on making a 3" down pipe to 3" cat, and then changing it down to 2.5" ? or should i go 3" all the way back,

or 3" DP to 2.5 cat all the way back

woot woot to the HMT crew

Edit : i tottaly forgot .....it's for my 89 mustang 2.3 4cyl

 

^^^ that ain't no ---- either