wait your lacking torque on an fa 50? please tell me your kidding. but what i have heard. simo shit on bottom decent up top. some vintage rando pipe that they stopped makeing in the 70's. it's amazing better torque all around and top speed. that being said i have seen one. and the guy who had it only had seen his also.
hack weld biturbo. all on the top decent for top speed. bottom end sucks. stock great torque sucky on top. that's all i have heard of.