How much power does it add to remove the Pre-cats(gutting them) and getting the SHO shop Y-pipe? I would also like to get rid of the res. Any help would be welcome.

1999 Silver Frost ATX Mercury Mystique

Mods:
Throttle Hang Fix
Fog Lite Fix
Gutted Air Box
Sony Xplode Head Unit
215/60/15 Goodyears
Hyperwhite Low Beams (9006)
Castrol Syntec Oil (5W30)