yeah, reamember that this isnt just the unit itself, there is a MAP sensor included (roughly $125), full plug and play harness, including harness for CDI box (believe it or not but the Mazda plugs required to make it "plug and play" are UBER expensive) and the time to make the harness, the base maps (think dyno time) AND the creme de la creme, a way to make this work without ANY CEL's and no gear tooth shaving!... think about it, and he is only charging roughly $500 for this over the rough estimate of $1600 or the EMS itself? you'd be insane to try to duplicate this yourself
*edit* not trying to insult anyone, just making a point