Definitely NOT worth buying a mivec controller. Mitsubishi did their homework when they set them mivec point. Hell they designed the cams, the designed the motor & computer to go with. People have 'lost' power fiddling with mivec change points.
If your looking for more power (which I think you are

) get an aftermarket piggy back ECU like a Unichip or equivalent.
Just remember - your gains will be in direct relation to the mods you already have

More mods, more gains from piggy back. I wouldn't bother with a computer unless I had at least done a proper CAI & some sort of exhaust work.