You can still blow apart your pistons with 5 psi of boost pressure if it detonates.
Install one of these kits to ease your mind on the piston issue.
http://www.alcohol-injection.com/water-injection-kits-1/pontiac-25/3800-stage-2-50.htmlWith 5 PSI maybe 170-200 HP @ the wheels,, just a guess though.
MBHD