from what i've read and from what jackson racing has researched, 12lbs of boost isnt going to be safe on d16 internals, at least not everyday driver safe.

i've got a d16y8 with the jrsc and the boost upgrade (9lbs). i've been told our motors can handle 10lbs of boost on stock internals, which i'm guessing is why jackson made the 9lb pulley and not a 12 lb. pulley. anyways my car is running well on 9lbs, i wouldnt recommend going higher.

then again i know a kid who is running like 9lbs of turbo boost and a 75 shot on stock internals in his cavelier. he doesnt care if he blows the motor, i think he's somewhat trying to (reason to upgrade), but the motor has made it through two bottles already??? very surprised its still going, but its going to eventually blow, and yours probably would too.