Couldn't find much info, but is your vacuum routed to this control valve for the egr?
find much info on the vacuum diagram for the egr valve on the CVT hx

 

36190-P2J-003 - Genuine Honda Valve Assy., Frequency Solenoid



Maybe?

 

This seems like it.

 

Is it hooked up correctly?

I am unsure of its function, if it is to aid in the egr opening, or to prevent it to open. It looks like one side of it is atmospheric to relieve pressure from the intake to the egr to prevent vacuum to the egr valve

 

Yes, it seems to be hooked up snuggly. Wanted to take out the hose on that side to measure the vacuum but wouldn't come off.
Also, the vacuum pressure on the intake side (feeding to this 'regulator ', felt higher. But it didn't feel as much at the ' Out ' side (feeding to the EGR valve). So it might be a dampened by this. Will try to actually measure it sometime.

 

The egr control solenoid gets activate when certain conditions are met.

 

Can they go bad? Can they be tested ?

 

Well from his description you can test voltage to the plug.

THe egr system on your CVT hx seems to be very similar to the civic VX (92-95). I would imagine trouble shooting it should be online somewhere, I'll try to search in a moment

 

Waited to see what happens before giving update.
The stumble got a lot better over time and some more after topping off the coolant and removing bubbles. (Lesson: don't forget the simple things). Now it happens over a lesser range of rpm (2 to2.2k), only when warm. And will have searching idle at stop light when warm. This eventually gets better the more I drive. If this points to something please let me know.

 

Still sounds like a vacuum leak on the intake manifold

 

Will try to look for leak using water spray... but this doesn't happen while in Park, only while running. So would the leak still show up?