You can add any condition just like in the following stat, that makes the stat work only with specific item types
<mul order="0x30" stat="pAtk" val="#other">
<and>
<using kind="Dual Fist,Dual Sword,Fist,Etc,Bow,Dagger"/>
</and>
</mul>
">
<and>
<using...
</and>
</mul>
there are usually 2 type of conditions, onCast and Stat
don't ever bother moding core for such things like removing effect on unequip because ull face other issues