It could very well be the upgraded chip....did the PO give you the original. You could have swapped it out prior to your inspection....next time.
Did you warm the engine and exhaust good and hot prior to the test? A good 'spirited' drive prior to help blow/clean things out probably a good idea.
There is a switch on the DME for different a/f mix settings/mappings.
http://forums.pelicanparts.com/showt...me+fuel+switch
Also check to make sure the O2 sensor is plugged in. The car will run in 'limp home mode' if unplugged. LHM mode is probably a richer mix to ensure no detonation.
Faulty head temp sensor could be fooling the DME to think the engine is still cold.