NOx emissions failure fix suggestions

I have a 1995 Geo Prizm that failed the NOx portion of Texas emissions by 219ppm. I was told by a mechanic it has no EGR valve which would have been my first idea. I thought all 1995 Geo Prizms came with one from the factory. I can see no indication that there ever was one. Also, my CAT is 3 degrees cooler at the outlet than the inlet under medium rpm in park (not under load). All other gases were low (HC, CO, etc.) So the CAT is obviously still doing something. I also have a broken line running from the Vacuum Temp sensor to the air intake. I had it unplugged and loose during the test because the plastic connector is broken at the sensor. I don't know if it effects NOx. So, should I have an EGR installed, replace the CAT, or maybe replace the sensor and line? Any suggestions?