Source: Complete Psionic
Choose a manifesting class that you possess. The powers you manifest from that class are more powerful.
Psicraft 4 ranks
Your manifester level f or the chosen manifesting class increases by four. This benefit can't increase your manifester level higher then your Hit Dice. Even if you can't Benefit from the full bonus immediately, however, if you later gain levels of nonmanifesting classes, you might be able to apply the rest of the bonus.
For example, a human 5th-level psion/3rd-level fighter who selects this feat would increase his psion manifester level from 5th to 8th (since he has 8 hit dice). If he later gained a fighter level, he would gain the remainder of the bonus, and his psion manifester level would become 9th (since he now has 9 Hit Dice).
A character with two or more manifesting classes (such as a psychic warrior/psion) must choose which class gains the feat's effect. This feat does not affect your powers per day, or powers known. It only increases your manifester level, which helps you overcome power resistance and increases the duration and other effects of your powers.
You can select this feat multiple times. Each time you choose it, you must apply it to a different manifesting class.