My take on the issue...

Kung daily driver use lang naman...

Intake-Headers-Exhaust (IHE) nalang gawin mo. Then change to hi-tension wires/iridium spark plugs/racing distributor. Lastly, better brake pads/shoes.

Ibang usapan na pag pang race/track use

This is what I did to my brothers car (1992 nissan sentra) before niya binawi saken. Pag daddy driving mode, kita mo talaga yng dagdag tipid sa consumption (nag +3 kms/liter sa normal city driving, +7 sa highway). Pag race mode ka naman, ramdam mo yng push to the seat experience (and of course, greater laklak sa consumption).

HTH