[Tofuboy]

The tech is right, NOx forms under high temp, but there could be alot of things that causes it.

Does your car has mods, if so, what are they?

Is your engine running hotter than it suppose to?

You said you put in a new radiator, but is it's valume equal or higher than your original one?

You can try putting a lower temperture thermostat (always make sure it is a fail safe thermostat) and that may help to bring down the running temp.

If your engine has EGR, you should check to see if it's working also since the EGR has alot to do to cool down the cyclinder temp.

Does anyone here know if the 88 CRX Si has air injection into the cat?

PS. Was the car tested on the dyno when being smog?