Thats a big Garrett turbo. Lightend fly wont effect much the performance if the car has a lot of torque.
with the 1.6 expect it reaching positive boost around 4500 to 5000 rpm, 1st or 2nd might not have efficient volume of air.
Try a v mount, cams, titanium valves and springs, bigger throttle(stay away from the 20v) for more response.
Grab a throttle of an old landcruser.