[fredjacksonsan]

I certainly understand you wanting to get to the root cause, but it might just be the high mileage. From what I've read while looking up NOX emissions, it seems it's from a lean mixture and high temperature in the combustion chamber. If you're not getting any ping or detonation, you might want to leave it be as your engine sounds like a good one.

I've heard of people putting 90% rubbing alcohol in their tanks to reduce emissions. It's worth a try at a couple dollars - much cheaper than a new converter every time the state inspection comes up.

Just reread the original post, and I apologize for not answering your initial question about the location /existence of the EGR valve. I don't know the answer to that, other than maybe go pick the brain of a friendly Jeep mechanic.