What, you're talking along the lines of 1bar+? That's going to pretty much need a bottom end overhaul. If you do that, you might as well drop in a B18B now and turbo that...it will produce much more power in the long run. You'll have fun with new sleeves, rods, pistons, a crank girdle (one a B series) would be nice, piles of stuff should be reworked for higher boost. We're talking a couple/few thousand into the engine itself to make it perform sweetly, reliably.