Greater Spell Penetration( Tome and Blood: A Guidebook to Wizards and Sorcerers, p. 40)
Greater Spell Penetration [General] Your spells are especially potent, defeating spell resistance more readily than normal.
Spell Penetration (PH) ,
You get a +4 modifier on caster level check to beat a creature's spell resistance. This supersedes (does not stack with) the bonus from Spell Penetration.