Perfect Spellcaster (3.5e Feat)
From D&D Wiki
 Perfect Spellcaster [Epic]
Choose a spellcasting class that you have taken Practiced Spellcaster for. Your spells cast from that class are far more powerful.
Benefit: Your caster level for the chosen spellcasting class increases by 4. This benefit can’t increase your caster level to higher than your Hit Dice. However, even if you can’t benefit from the full bonus immediately, if you later gain Hit Dice in levels of non spellcasting classes, you might be able to apply the rest of the bonus. For example, a human 15th-level sorcerer/7th-level fighter who selects this feat would increase his sorcerer caster level from 15th to 22nd (since he has 22 Hit Dice). If he later gained a fighter level, he would gain the remainder of the bonus and his sorcerer caster level would become 23rd (since he now has 23 Hit Dice). A character with two or more spellcasting classes (such as a bard/sorcerer or a ranger/druid) must choose which class gains the feat’s effect. This feat does not affect your spells per day or spells known. It increases your caster level only, which would help you penetrate spell resistance and increase the duration and other effects of your spells.
Special: You may select this feat multiple times. Each time you choose it, you must apply it to a different spellcasting class. For instance, a 20th-level cleric/17th-level wizard who had selected this feat twice would cast cleric spells as an 28th-level caster and wizard spells as a 25th-level caster.