koren: I'm not sure what you can do, but i've had a friend last time who shave off some of his cylinder head to get a little bit more compresion. but.. what petrol do you use in singapore? if its the same as us here using RON97 i don't think it is wise to use too high of a compresion ratio unless you can tune the ignition timing and stuff.
and since toyota's vvti ecu is too "clever", you can't really use any piggy back computers too. so, for light mod, change your filter to a hi flow drop in type replacement air filter, check out K&N, they got alot of them but not sure if they have any for a vios or not. Do not get open cone or open pod filters since they might just suck in more hot air if you drive around slowly (assuming you're always in traffic in sg).
exhaust system you can do abit of research on the net, since i'm not too good with automatic transmition exhaust setup. most people just say use S-flow muffler or stuff..
or for serious mod you can try find an aftermarket fully programable ecu to get thigns started. engine internal can be custom made but i'm not sure where you can do that, try phone crower or something lol.
