it would be easier and cheaper to transplant a 4efte engine than to do a conversion. you could try sourcing engine from fensport, not sure on the price, best to get in touch with them. as for power, a standard 4efte produces 133bhp.with exhaust, decat and filter probably something like 145. with boost controller and fmic + upgraded fuelling somewhere in the region of 170-180 i should think. don't forget that the key to a gt turbos performance is power to weight, i don't know how heavy a corolla is but im guessing its more than a starlet.so prob best to make the car lighter as well.