[gofstbuick]

Those readings look really rich. But once you drop the CO down, NOx is going to go up more. Because you don't have the luxury of a functioning EGR system, you may look for a three way cat from a European vehicle. Most European engines are not equipped with EGR and they reduce NOx with a three way cat that has a lot of surface area. Look at the cats on a 4 cyl Porsche (for example, 944 or 968) and you will find a their cat is twice the length of most domestic and asian vehicle cats. If you also have the O2 and CO2 readings, you can plug your results into a Lambda calculator to determine how rich or lean your engine is really running. then you can adjust your emissions to perform most efficiently and then as others have suggested, add a good cat.