Another update for anyone following...

I finally have the wideband hooked up and working correctly! I hooked the white signal wire to the MS unit and the black ground to it's own ground (NOT MEGASQUIRTS GROUND). The AFR reads identical on my guage as it does on Tunerstudio. The slowly rising AFR doesn't happen anymore either.

I started the car and attempted to tune idle by adjusting the injector characteristics a percentage and millisecond at a time (just as the manuals say to). I eventually got a decent idle but it got worse as the car warmed up. I continued tweaking and got a smoother idle but it had a slight oscillation.

Additionally, the car would studder when given throttle. The AFR's would richen and the car would almost shut off before the RPMs would raise and continue running.

I decided to check the IAC valve that was now hooked up thinking that is may be the issue. I took the throttle body off and used the IAC test mode.

No luck.

I then remembered in Evan's youtube video and in the manual it stated that the polarity of the pins might be backwards. So I made some "jumper" wires to switch the polarities of the plug. No luck. I tried every single combination of the IAC plug and never got a single bit of movement.

Am I missing something here? Is there a way to test if the MS unit is giving the sensor the signal it needs? I have Tunerstudio set to IAC Stepper Moving Only. Do I need to tell Tunerstudio anything else about the sensor? Is there a place to do so?

Could the fact that the IAC is slightly open have to do with the studdering on throttle?

I have to say the MegaSquirt is getting extremely frustrating to me... Extremely...