Good job on gettin' her goin!! 👍
The idle flux could be an EGR issue.. Check all related vac lines and make sure the diaphragm on the Y-pipe is working correctly. I'd guess the almost-stall symptoms are what is making the volts drop on that stumble.. Its common for the V6's to have this trouble..
You could also check the Idle Air Control Valve.. Pop that out and make sure it's clean and looks ok.
Also, if you had disconnected the battery for your tune-up stuff, make sure you get it out there and run it over 40mph for a bit to get the ECM back in touch with all the engine sensors. Then let it run at idle for a bit, up to temperature and see what happens..
You might get lucky and it'll toss a check engine code, and that'll help a lot..
[This message has been edited by Indyellowgt (edited 03-08-2016).]