As it is now this feat does the following;
Power Attack Feat
This feat allows you to make exceptionally powerful, if less carefully aimed,
melee attacks. Once you have this feat, you may enable it or disable it at
will, using COMBATMODE +power attack and COMBATMODE -power attack. When
active, you fight aggressively, with all your might; this reduces your chance
to hit, but greatly amplifies the damage you deal out when you do hit.
This feat has a pre-requisite of a high strength.
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Bringing this feat closer to the D&D rules and making the use of two-handed weapons more attractive, the modification would involve the following; whenever you use a two-handed weapon or you use a one-handed weapon in both hands with this feat, the bonus to hit subtracted is added TWICE to your bonus to damage. Furthermore you don't get any bonus to damage (no matter if using this feat with two-handed handed weapons, a one-handed weapon in two hands, a one-handed weapon weapon in each hand, or a one-handed weapon in a single hand) for those weapon(s) you are using if they are light. Example; holding a short-sword of your size with two hands will not give bonus, but if you are dual-wielding a longsword and a shortsword, both of your size, the longsword would get the bonus but no so the dagger, but the penalties to hit still would apply to the shortsword in any case.
http://www.d20srd.org/srd/feats.htm#powerAttack