Toyota Repair: Nox emissions to high, corolla dx, nox emissions

Question
I have a 1994 Corolla DX and it will not pass inspection, the Nox is a little to high on both 15 and 25mph. I do have a broken TVV that I need to replace but I was told that does not effect the Nox. Does it?

The car did sit for about six months with no driving and the same gas. We have put new gas in and RXP gas additive and it helped the Nox get closer but not quite. The nox failed by 231 points. What else would cause the Nox to not pass?

Answer
Higher than normal NOx emissions are caused by an inefficient EGR system, the system needs to be tested to see if it's working normally and if not the cause should be diagnosed, another reason may be higher than normal combustion chamber temperatures which could be caused by incorrect timing or excessive carbon deposits in the combustion chambers which will raise compression and cause higher NOx.