EGR valve appears to be able to flow, cooling system working properly, and a new exhaust manifold with CAT has been installed. on dyno nox is between 600 and 800 ppm. when egr is disconnected the the nox drops to between 0 and 50 ppm. I have verified the erg temp sensor drops below .5 volts, so flow appears o.k. What else should I be checking?

Cars & Trucks - Nissan