Indeed I have not tested fuel pressure.
Part of the issue here is I really do not know what this NOx number actually means. It is the limit the state of Colorado has somehow determined. If I am over it does it mean my truck is actually lean? This is why I am thinking of getting a wideband so I can actually know what is going on. Determining that a motor is lean by NOx is not very rigorous. I am certainly not so lean that I have a miss or pinging.
As I was mentioning, my previous truck now owned by a close friend - (30k on motor, DT and open exhaust, 252S cam) just barely passed the NOx, and that was on the third try. After the first try failed we retarded the timing a bit which got NOx down but it still failed. He then bought a new catalytic converter and it just squeaked by. It's possible that all of that change was due to driving differences by the tech, as the catalytic was fairly new and put in by me when I owned the truck.
EDIT: I never tested the EGR for my friend, I will try to do that in the next few weeks and see if his is also not doing anything.
