How much boost does that turbo make right now?
I wouldn't mess with it. That's a wiffle engine. The turbo makes it driveable, it runs cooler and more efficently. It's never going to be a powerhouse and you risk overspeeding the turbo or scattering engine parts.
If you wanted to mess with it, first you have to figure out how to turn the fuel up. Increasing the volume in the injection pump chamber is probably how you do that. There's a screw in the rotor of my DB2 that does that. I don't know how yours would work.
Then, you have to figure out how to adjust the wastegate. If you turn the screw up and inject more fuel, the turbo would spool up more quickly and hit the blowoff valve more quickly--then you would put out black smoke because there would be no additional oxygen to consume the extra fuel with. If you did burn the fuel, the turbo would speed up even more making more air available, making more exhaust gas, speeding it up even more. Without real knowledge of the setup, overspeeding would be a real risk, as would blown head gaskets, damaged crank, maybe overheating. And for what gain?