to get power out of it the engine will have to come out for the work to be done, at that point it's far easyer to put an engine in thats willing to be tuned.
the cheepest way to get power without removeing it is buy a megasquirt, 2 headgaskets and a turbo or supercharger, have fun fitting it enjoy the 200 hp till it goes bang.
or buy 16v, turbo 2 headgaskets arp bolts a megasquirt and enjoy the 300 hp then get forged internals and a bigger turbo