While it is possible to "fix" blown coils with good coils from a donor unit, there is a risk to the ecu from a bad IAC. I'd buy the new style IAC from the site above and forget about the problem. I think I paid about $135 for mine. OEM mitsu part and box, looks diff but works just fine.

The 3.0 has two idle air controls.

One is the FIDLE valve, a thermostatic, unservicable initial fast idle valve that closes as soon as the coolant temp starts to rise. It's built into the TB, and you can't get at it. Bad FIDLE means new TB. The other one is the IAC/ISC, which you've had out already.

I'd reinstall the "new" JY IAC and disco the battery for at least 10 seconds to clear the ecu memory, then let the ecu relearn the new IAC and see if it settles down.

You may also have a failing ecu coollant temp sensor, and not be getting full cold start enrichment from the injectors. That would cause a lean stumble, and perhaps a hard start.