[new echo owner]

Just curious, what are you trying to accomplish moving the VSV?
Why do you think the VSV or the EGR is the cause of the irractic idling?

 

[new echo owner]

I'm guessing ease of access - that VSV is mounted underneath the Intake manifold from the factory: it's a PITA to get to. Moving it up onto the firewall makes access / diagnostics much easier. (BTDT here.)

Can understand if the VSV needs to be connected and disconnected often, or if the old one is bad; however, base on the descriptions, it is not the case.
If OP wants to check if the EGR system is causing the idling issue, can simply disconnect the vacuum hose to the EGR valve itself.

 

[new echo owner]

How long do you have to drive the vehicle before this condition happens?
In general, EGR related issue only happens when the car had been driven on the highway for extended period of time; meaning the EGR valve had stayed opened for long periods of time.
If you want to eliminate the EGR system as a possible cause, just disconnect the vacuum hose to the valve, and drive the vehicle; if it is related, the idling issuse won't happen.
There are other casues that could affect idling, sticking injectors for one, especially with a vehicle that had been sitting often!

 

[new echo owner]

The one that goes to the EGR valve itself, just disconnect and plug the hose! In other words, don't even allow it to work!

 

[new echo owner]

Alright, so further updates;
I installed the new EGR VSV and relocated it onto the plenum. When I fired up the car the problem came back unfortunately, though it felt slightly less severe. I’m going to clean my EGR and investigate the booster.
I’m hoping it’s not an electrical issue somewhere making the EGR act up. When I unplugged the vacuum going to the EGR, the car ran perfectly.

Does your car have a EGR modulator valve? Make sure that is working properly, and the hoses are connected correctly!

 

[new echo owner]

Sounds like a sticky EGR valve condition, not closing completely! Usually happens after extended high speed drives. Just a guess!

 

[new echo owner]

Nah, would try cleaning it first, would be sufficient most of the time, at least won't hurt trying before spending more money!

 

[new echo owner]

Got it! Just a suggestion; nevertheless, keep the old one around as a spare!