It can Kinda/Sort work, but not like he says..
I attempted something very similar. I put in a 20k ohm Pot in series with the IAT on our '92. I was trying to get it to richen up the mixture by making it think it was cooler out than it was.
The IAT reads about 16Kohm @ 100F and 53Kohm @ 32F (give or take a little of course).
I was trying to richen up the mixture a hair to try and get rid of pinging (barely pinged, but was anoying), but of course @ the time I didn't know it would also increase the timing (so it didn't help me)..
It is a common trick used on mustangs and if you want to do it, just get a 20K ohm resister and put it inline with the IAT. Now you have what he was selling on ebay.
When I had mine in, I "thought" i could fell a little difference, but mainly in initial punch (off the line), but thats it.. It didn't hurt my mileage but since it wasn't really helping I have it turned back (I have the pot set to not change the setting of the IAT)..
One day when I'm bored I will turn it again and actually try to measure if it really helps..
~Mark