there is a cheap way to supercharge a ka. i thought up a kit, but never got a chance to install or test it. everything you need shouldn't be more than $1000 total. well maybe more than that if you get a rom tune. and one draw back is you can't have a/c. parts you will need:

sc14 toyota previa supercharger (also a 2.4L 4cyl) 200-400 bucks
stock sr injectors 100 bucks maybe
z32 or maxima maf 100 bucks
stock sr side mount with piping 100 bucks
rom tune

so all you need to do is take off your a/c compressor and make cool custom brackets to bolt the supercharger where your a/c used to be. so this way you can utilize that belt to run it. run piping to a stock side mount, then right to the motor. the only uncertain thing is how much boost it will put out due to the possibel size differences in crank pully diameter's. but at 8psi it should put out over 200 whp. another awsome thing is the toyota supercharger is a sealed unit with its own oil supply, so no need to run shitty oil lines.