i dont think the stock internal can hold a 450hp blown car for a long time that is going real close to the edge, everyone who has a blower keep it in the 400hp range and that is still considered pushing it
you're tune sucks. i have an automatic making over 400rwhp with only 2 more psi. i still have the stock heads, cams, and lower intake and no intercooler.
Those are included in the vortech kit. I would suggest looking at www.modularpowerhouse.com and checking out their mongoose ktis.
You can get the vortech kit for well under 4 grand and it inlcudes everything you need, injectors, new fuel pump, tune, supercharger, brakets, etc. Its one of the most if not the most complete kit on the market.