Super inconsistent idle all of a sudden (vid)

[silence2-38554]

Hey everyone, over the weekend my girlfriend & I removed, cleaned (thoroughly) and reinstalled her IACV ('90 auto Legacy L). We replaced the oem stamped metal gasket with a rubber fiber gasket (traced & cut out ourselves from a larger sheet). Our initial goal was to try to get the car's idle more consistent, and it seemed to work for the most part. We're also trying to make the idle smoother, as it is extremely rough. Through researching here on the forum, we noticed that the knock sensor has 3 small cracks in it & plan on replacing it asap. Thing is, all day yesterday, since cleaning the IACV, the idle has, at the very least, been consistent. Today, all of a sudden, the idle will shoot up to 1800 rpm, then drop very low, as if to bog & die, but manages to barely hold on only to shoot back up to 1800. Check out the video link here:

http://gallery.me.com/kristopheryates/100114

Keep in mind that the accelerator isn't being touched at all during the video. Does this seem like a vacuum leak? What's more annoying is that it doesn't do this all the time, either. It will idle just fine for 5-10 minutes, then start doing the rev/bog dance again. What should I be looking for other than a vacuum leak? Is it possible that this is also related to the bunk knock sensor?

[stipro]

TPS??

[Jessekrs123]

If you have not figured this problem out yet, the knock sensor would be your first step. It is weird how it is idling like that with no CEL relating the TPS, or IACV so it is possible that it is something that has nothing to do with any sensor. My car did this for a while, but I got the code for the IACV, I replaced it and it still happened. My problem was a bad ECU ground, but I grounded that and now it runs mintly. I would check electrical connections, vacuum leaks, and grounds in the engine bay, make sure they are not extremely corroded or loose.