After Market mods.?
You don't hone pistons, you hone the cylinder. You will need stronger connecting rods, stronger crank, a stronger drive shaft and differential, etc. To run 30 psi is just ridiculous and asking for trouble, or too much of a price tag if you do it right. Honestly, scrap the LS motor, get a GS-R bottom end (basically the bottom end of the block, crank etc) and mate it with SI heads. that way you get the torque of the GS-R and the horsepower of an SI, that LS peice of junk will get you no where, especally the horsepower you want.
I'd run 14 psi if I were you. I've seen major problems with people running over 20 psi.