Too much O2 will cause the NOx to go high. Very high. Probably something to do with your air injection or an exhaust leak.

Advanced timing will also cause high NOx.

Set your timing according to hte manufacturers specs, replace your plugs with whatever the dealership parts department supplies, fix the broken stuff, change the oil and you should be good to go.

It sucks when you GP a car.

Clay
(currently employed as a Kaliforia smog tech)

1990 Montero RS (In pieces... for now)

KG6VNX