The MA limit for NOx is 3.00. My 1984 380SE had a reading of 3.46 and failed. I have tried Techron and I also replaced the EGR. The next test came up at 4.47....a whole point higher!!! So, I had the catalytic converter replaced...latest test is:...........4.71!!!! Even a bigger failure.

Any suggestions on how to bring down the NOx on this CA emissions car? Thanks!