You won't gain anything at all; if you're that desperate for 1-2 hp, you're in the wrong ballgame dude. Leave it on and avoid converter failure, plus an occasional code or two.
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Capri306, Moderator, The Mustang Works Online
1979 Mercury Capri, 5.0L -- C4 -- 2.73
1987 Mustang LX Notch