Go onto 480 europe, the old skool way was getting a "RichMod" ECU, done by Rich Pruen but he left the scene for a few years. They still come up though if you keep your ear to the ground.
Check this thread. It's about my 343 Turbo. It also has the B18FT engine.
I changed the stock-ECU with a programmable one (similair to MegaSquirt)
But You can also do a rich-mod (just google for it). Than You can go up to about 170bhp max.
Than it is time to get another turbo, injectors etc. etc.