Quoting strokin4dr:
There is no wax plug.
So i have taken apart five different TBs, and looked at the FIAV, and I am really confused on this whole wax plug thing...it seemed to me to be more like a thermostat, where you have a temperature dependent spring height that can be adjusted via the screw deal under the freeze plug. Although, if trying to adjust be careful because the plastic adjuster gets brittle after a lot of heat cycles and causes it to break apart when you adjust it.
To OP:
I recently had some similar issues and I would recommend doing the easy checks first. I would check for boost leaks at your TB, any extra air getting from the turbo side of the TB to the Manifold side will cause your idle to freak out. Check for vacuum/boost leaks!!! I literally put four different TBs on my car in the process of trying to fix my idle. A BL tester, if you don't have one, can be built for about 20$. You can guarantee that it is not your TB if it tests fine. Furthermore, make sure to remove your ISC and check the gasket. This can cause your idle to get screwey as well. Pull out your trusty Voltmeter/ohmmeter and check the resistance and voltages on your IAC/ISC, TPS and the pigtails they go with. You can find the correct values by looking on tuners, reading your FSM, or just googling it. After that, if you have checked everything and set you BISS properly while fully warm, and still have issues, I would think it is your FIAV, and you can either block it off or get a rebuilt TB. I have my FIAV blocked off and the ISC does a great job of taking care of the idle when cold. If you are attempting to remove the FIAV screws on a stock TB, know that you will probably strip the heads. I used my Dewalt 20v impact/drill and got 4/5 out fine, but had to use an easy out on the last one. You may want to get some new screws in advance.
To sum it up I guess I am saying that if you don't have any codes, there are a lot more common things that will go wrong before the PCM. I would check all of those before starting at the PCM. The PCMs on our cars are pretty solid as long as the Capacitors are in good shape. If you have Link, you probably have good caps, and the ecu was tested before getting sent out from ECMlink...
hope this helps and anyone feel free to correct me if I went wrong somewhere!!!
Cheers
-Manik