Nicely said Niky! galing talaga!!!
*TS, if you want to play on the "safe and tipid" side, i'd say go for upgrade IHE (Intake Headers Exhaust) on your stock engine. This at least is a little less invasive. It will give you a slight power gain. Pero kung gusto mo nga ng talagang oooomph, change engine is the way to go.
You can also opt to change your spark plugs and Hi Tension wires to split fire.
Econo upgrade ika nga. :D hehehe di ko lang alam how much 'gain' you will gain from this...