OK, it's not their fault my car blows high NOx, but busting my chops for license plate and side marker lights which supposedly went out in the last 4 weeks is being ultra-picky. Now, I'll be dropping a bunch of money that I would rather spend on headers on figuring out why my NOx is so bleepin high. I don't get a code, and I yanked the egr valve and tested it as best I could. Pushed in on the valve to make sure it wasn't stuck, could hear air coming out of the vacumn port. Perhaps time for a holley tbi manifold while I'm at it. I found this link which gave me some things to think about http://smogsite.com

Dan
'91 RS all stock

 

The valve can work fine, but if the passages in the manifold are plugged with carbon, the valve won't be able to do what it was intended to do.

You might consider pulling the manifold and cleaning all the passages out. My LG4 managed to pass (just barely), but when I pulled the manifold to fix a coolant leak, I found those passages were plugged. Magically, I could now advance my timing without fear of pinging - indicating the valve was not working properly before. When next tested for emissions, NOX was fine (although hydrocarbons were borderline still - cat).

All of this was before the mods in the sig.