basically the miss firing system miss firers per cycle, so it does not fire a coil on each cyclic. it is set on rpm so you can have the system engage between 3000-4000rpm.
real antilag will also retard the timing when it doesnt fire a coil in the cyclic
the brand of mine is GRiD its a Japaneses company, i purchases it brand new cost was $600, but it had to be sent back to japan as it had issue working with the pfc so they had to rechip the unit which cost me an extra $300. in the end i don't really think it is worth it, your better of spending the extra $900 in a good ecu which can handle antilag