I agree with the first two replies. On perfect tuned and maintained stock B230FTs, people have run up to about 14 psi. In fact, Volvo used to race a 745T with 14 psi that was otherwise stock. My guess is that the motor would make about 210 hp then. I think the fuel system might support a little more power - like around 230 hp -- but I don't think the ignition has enough retard authority to reduce timing sufficiently to produce that power without pinging. Water injection will help a bit, but not make a dramatic difference. You need to do other modifications. These are detailed at the Turbobricks website. Do some research before you squirt water in the intake and run really high boost. I know it is an old racer's trick, but the old racer was not running an 89 B230FT. Stock internal and bolt on parts have different headroom levels from one engine manufacturer and engine model to another. At some point in the 89/90 timeframe, Volvo started putting stronger connecting rods in the B230FT. I don't know what month. You may or may not have them. The newer rods are significantly stronger and engines with them can take more boost. Even the newer rods can be bent, however. Volvo hotrodders are too few to give you reliable testimony as to when you will blow your specific motor. If perfect, I think you could run 14 psi. With a good selection of mods, you could run more, but you should accept the risk that problems could arise. I ran 18 psi on an 89 B230FT for a while. The motor was pretty loose when we pulled the head at 117k miles, but it had that diesel like sound on cold start when I bought it with 85k miles, so maybe I had a loose motor to begin with. Do a compression leak down test. Then research a lot, test a lot, accept the risk, and have fun.

Philip Bradley