The NO max here at 25 mph is 903 and I had 1074.I passed CO with.01 at 15 and 25 mph, but the examiner said it was too low and I had to have a vacuum leak. The vacuum system isn't that complicated and I was able to verify that nothing coming off the vacuum manifold was leaking. Then I sprayed brake cleaner everywhere while it was running to no effect. The only thing I can't find is where vacuum goes into the cab for the heater/AC.
Then today I checked the vacuum solenoid and found that it is leaking a tiny bit of vacuum to the EGR. Is that a leak that will affect the NO?

 

Hey philetus, I know you updated your thread today, but it's gone,although it shows two posts and this will be three. So you got a gage and checked the vacuum and has a steady 20. I'd say you don't have a vacuum leak or it's fixed.The solenoid is probably ok.
You probably didn't even need to ask on this forum and that's good because nobody was going to answer you anyway.

 

EGR(exhaust gas recirculation) system is there to lower NOx when engine is under load, so a vacuum leak in the EGR system could prevent EGR valve from opening enough, so higher NOx and then extra air coming in, lower CO

High NOx can also be caused by carbon build up in the EGR Valve and tube from exhaust manifold, this build up reduces the exhaust flow into intake when valve opens.
This can be cleaned by removing EGR valve and tube.

High NOx is cause by high cylinder heat which happens when you accelerate or go up hill, engine under load.
The exhaust gas actually cools the cylinders, as odd as that sounds, lol, it also reduces the chance of pinging/knocking.
If you ever get pinging/knocking you will also have high NOx as that raises cylinder temp

 

I took off the EGR and the tube. Both of them and the hole in the head are clean and clear.I have a new gas filter, fuel regulator, oxygen sensor which I'm going to install when my New Cat arrives in a couple days.I ran a can of Seafoam and then a can of CRC Guaranteed To Pass through the system and I will fill up with Chevron or Shell Premium before I go for my retest and I'm hoping all of this together will get it passed.Thanks for answering.

 

Yes, that should do it.
Be sure to drive at least 20min before test, engine needs to be warmed up.