Bought a Crap Gimmick -- What does it do?

There's all sorts of "performance" modules out there..

if it's the air temp; by telling it it's colder than it really is; more fuel will be dumped in (air will be more dense, hence requiring more fuel).

there's ones that do O2 sensor mods -- basically they lie to the computer to get the computer ot pump more fuel in....

anything short of modifing the injection map and / or ignition map is a waste of money .... That's just my HO

computer to get

So, if it works by claiming it's colder than it really is, could that lead to the engine overheating?

I realize that's probably an incredibly naieve question. More or less everything I know about cars, I learned from my dad, who couldn't keep up any more by the time fuel injectors were a serious option.

I'm not even exactly sure where to hook this thing up. My repair manual hasn't been much help (At anything, really. I've always preferred Chilton, but I can't seem to find one covering the '98 Legacy, and had to go with Haynes instead, which I'm sure is a fine manual, but it's awfully thin for the number of models it covers)

Move 20 bucks from your pocket to his :0

doubtful; more than likely you'll just notice your fuel usage go up and your spark plugs foul faster -- you may eat up a cat quickly too.

I would advise you to toss it out.