The pipe sizes on an SE are 2.25" all the way through.
The SVT is 2.5 at the Converter, and drops to 2.25 on each pipe after the split.

You need a muffler, either in place of the resonator, or on each of the pipes after the split.
Most people put a high flow glass-pak in place of the resonator, and replace the rear mufflers with pipe.

I dropped my exhaust and replaced it with a used SVT exhaust, minus the resonator.

SOUNDS GOOD...mmmmmmmmm

Pete...

98.5 SE Sport Duratec ATX (P66L)
Black Clearcoat on Greystone
DOB 11/21/1997
DOP 12/25/1997
PIAA 510 Super White Driving Lights
SVT CAT-BACK EXHAUST (No Resonator)
DiabloSport Chip (LPQ4) - Engineered To Raise Hell
Too many other mods to list...
Sounds sweet, runs quick...
Crazy Horse Dyno @ 121.4 WHP/129.6 TQ