Hasa68mustang --
Forced induction is a power multiplier, so you need to know the base HP of the engine being boosted to get any kind of answer. If you go through the calculations assuming common VEs, Compressor & Intercooler efficiencies, etc., 30 pounds of boost has the _potential_ of giving you a 260-265% HP increase. So, if your base motor makes 100 HP, 30 lbs of boost should give you 260-265 HP. A 200 HP base motor could potentially get to 530 HP +/-. Note I said "potentially"; there's a lot of wiggle room and assumptions to come up with that figure.
But I believe Evan put it best: It's a buttload of power.
However, with the intercooler running at 75% efficiency on a 75 degree F day, the intake temp would be around 150 degrees F (as an aside, if you tried 30 lbs boost without an IC, the intake temp would be close to 350 degrees F. If you piped it away from the intake, you could cook your next Thanksgiving turkey using the turbo as the ulimate convection oven...). Finally, using general rules of thumb from Ak Miller and Spearco on boost vs octane vs detonation needs, this motor at 30 lbs of intercooled boost will need a minimum of something like 114 octane to avoid detonating itself into the history books. Certainly, the factor I've left out is how long the engine will be at maximum boost (the longer, the more danger), but you get the idea.
And that's not saying anything about the engine being able to hold together mechanically due to high kinetic forces.
Hope that helps.
--- Barrett