My VX had low idle and sometimes a few minutes of high idle.
The idle issue is solved, but I do not think one item was causing it, here is what I did and learned.

The idle started getting lower about 6 months ago, it ran good but started working its way lower until it was about 500 rpm. Also once in a while the idle would go to 2500 rpm and would go up to 3000 rpm and down to 1500 rpm but would not drop down unless I shut it off for a few minutes.

I decided I needed to figure out what was going on before it stopped running. I started with replacing the IAC and the idle came up to around 600 rpm, then I cleaned the very dirty throttle body and PCV as the store did not have the PCV in stock and the grommet fell apart when I pulled out the PCV so I had to find something that fit as nobody lists a grommet for the VX or the Trooper.

I found the Dorman #42058 PCV grommet for a Toyota is an exact fit for the VX.

After that the idle was up to around 700 but was a little inconsistent so I had the battery checked and it was bad, so I replaced it and the PCV and grommet and now it idles around 1000-1200 when cold then settles down to 750-800 when warm and runs smooth.