Lower the compression ratio. If you get the compression ratio down to 17:1 (I think the best way is to get slightly shorter pistons) and replace the cylinder head bolts with studs and nuts, you can safely get the turbo boost up quite a ways (possibly past 30 psi). With that, you can increase the fuel output.

Installing water injection will help lower the EGT's, allowing you to add still more fuel without damaging anything (if done right). Propane injection is also a possibility.

If you try any of these things, the first thing to do is install an EGT and a turbo boost gauge! Then follow them religiously...if you mount the EGT thermocouple before the turbo, make sure the temp never gets above 1200°.

There's more to it, but those are some of the basics...