Crap...
High nox, passed 2 yrs ago when not on rollers, this time failed nox...
Only changes were fuel tank(which passed lol), hei dist, cold air intake
shop said possibly egr or pcv, currently egr isnt connected(wasnt last time), any ideas.
Im going to make an egr tube, but any other ideas before I take it back?
Fyi, 4.2 with 4.0 head, howell injection, hei, and new cat currently