it controls the idle valve cycle, meaning how fast it opens or close, it'll then control the air flow when you idle. i cant really elaborate further as i myself isn't too sure, but i can tell u, once u use hondata, your idle will be smooth.
currently i am still running on hondata. but it doesnt belong to me. my mech is doing some major cosmetic job on his car, so his car will be out of service for a couple of months, meantime, i make sure his hondata is still warm.. hahha
1.8k is a very very good price. u cant get that here in KL. but then again i would like to warn u about car parts and when they are super cheap, something's fishy.
i'd rather pay the regular price and buy it from a reputable/respectable seller cum tuner. so if anything goes wrong, he can sort it out for u, rather than seller blame tuner, say his tuning wrong, make your ecu spoil etc etc... u know la... everyone doesn't want to take responsibility.
if u want a good tuner from KL, i can recommend mine, but price wise cant fight the one u linked to me la. rest assured, my tuner will sort u out until you are satisfied.
=)