Much more too it than that...more boost means you need a fuel system to support it. So, bigger injectors, fuel pump, probably need to convert to a return style setup, run high octane gas....blah, blah, blah.
The motor is stong...but only the crank is forged...meaning, under detonation or high cylinder pressure, the block just can't take it. When Ford released the new 03 Cobra with a blower already on the car, they forged the pistons and rods from the start.
To forge your motor, you would have to take the motor out, send the motor to a machine shop to bore/hone it, stuff it with forged pistons and rods (reusing your crank) and reassemble the motor (simply put). Now you can run a little more boost, more timing, and be a little more aggresive on the tune to get more power.
I was running 13 lbs of boost. Boost isn't the only thing that makes power when talking superchargers...it's a big part of it, but a lot of other things come into play.
Oh....16 lbs of boost is getting on the wild side on a street car usually.
Cost to forge your motor; depends. If you have a shop do the labor and parts, around $5500. Yourself, $4000 or so. Depends on how much you want to put into it.