Is there an easy way to tell if a car I'm considering to purchase has an upgraded ECU chip without driving it? What does the "stock" ECU chip look like?
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Jim - 1996 Platium Limited Edition, tower brace, hitch, tinting 101K miles

The only clue is that it "should" also have the upgraded performance exhaust system, the ECU upgrade isn't too useful without it. Otherwise, since it's just re-programming of the original Volvo ECU, it would physically appear identical. There "might" be a sticker on the upgraded ECU, or might not be, most wouldn't be interested in advertising the upgrade to Volvo service if the car were still under warranty.

-Punxsutawney Phil

You really can't tell unless you remove the ECU from the control box and pop open the cover. Maybe a private seller MIGHT let you do that in order to close the deal but I don't know if a dealer would let you do that. If it's a soldered on aftermarket chip then usually what they do is solder on an eprom bridge or adapter (I don't know the exact technical term for it) and the aftermarket chip sits on that. You simply CANNOT tell on an IPD flashed rom ECU though because there are no physical signs, it's just software that has been downloaded onto the stock ECU.