on stock wira? better not la. the thing cost a bomb, but hp/torque increase not much. 20hp sure is lie. better use that money to change bigger piston and rebore ur block, for bigger displacement. sure more worth it. or save a bit more, do bolt on turbo.
from my experience, when u have engine that is more powerful, FC sure is high when u tekan laju2. but when drive normally ( no sudden accelerate and breaking, speed around 90-100kmh) FC become more economical (save).