i can't remember anyone in oz coming across the JES brand,
seems they are fairly small - google only shows one reference to them,
which is just text on a japanese skyline owners homepage:
http://www.geocities.jp/zxe11441/engin.html
translates as:
"It is something of the mail order, SHOP JES (Japan electronics service). With mail order 30,000 Yen.
Because the reason which it selects reputation was good with the article of ap and CARBOY. Of course, also price is cheap"
he says a bit more about rom writers,
which could suggest it might even be a daughterboard thats sold with blank eproms made for self-tuning.
(you could try pulling the chips out)
but basically - the 180kph speed limit probably has been removed, the rev limit might have been raised, and it will be a more agressive fuel/ignition map
(which might have supported mods like bigger injectors or turbo that were removed before sale)
you could download the rom file to your pc and use romtune to compare it to a standard map,
but if its "massively overfuelling" and its probably not set up for the currents mods, and most likely be better just removed...
