Fed up erratic idle

Here is my story. I rebuilt the engine and got it started after the reassembly. It is my 22 year old daughters car and I really want to get it back to her but I also want it running right. The idle prior to overhaul was erratic. I have had only one check engine light issue and I resolved that. It was an ECT sensor connection. I have replaced the throttle body on the D15b injector, which replaced the map sensor and the air flow sensor. I have put in a new ECT sensor and a new O2 sensor. I have new plugs, wires, and though the engine runs it idles very erratically. I have bled the coolant to ensure no air is in the system. There is however a piece of the back of the injector that has vacuum line to it from the bottom and one on the top. There is a two wire electrical connector, it mounts with one screw and has a circular vent of some sort on the top. I don't what it is or does but it resembles an EGR valve. Can anyone tell me what it is for? NAPA couldn't figure out what it is and I am lost. Does anyone know what I have missed to stop the erratic idle? Please help me out!

erratic idling:

tps? map? iacv? vac leaks?

There is a two wire electrical connector, it mounts with one screw and has a circular vent of some sort on the top. I don't what it is or does but it resembles an EGR valve

post a pix.

Talked to a Honda dealership and they tell me the unidentifiable part is a "Purge Cut Solenoid Valve". Whatever that is.

I own 6 hondas - three civics and 3 accords. ALL of the civics and one accord have suffered from this surging or erratic idle and I have resolved all but this one. I am miffed and wish someone had a fresh idea that I haven't tried. I am 300 miles from a Honda dealership and getting quality repair service in my area is almost impossible.