Boosted brothers, Any one know where this washer goes? Diameter is roughly 1.25" . I'm probably about half way through the TRD SC install on my 2006 Xrunner. The only place that makes sense for this washer is on the backside of Idler No. 1 (the one at the bottom that we have to tinker with) based on the bearing/rubber configuration and how it's very different than idler no. 2. I've been very careful up to this point, and never heard this washer hit the ground as I removed both of the idler pulleys. I found this washer when I climbed under the truck recently to tighten the radiator drain valve. Any help would be most appreciated or scanned pages of the Factory Service Manual. Note: This washer is not the same as the two thin washers portrayed in the following diagram. I have the thin step washers and confirmed they were re-installed per the diagram. Plus, these two thin washers are a bit different from the washer that I posted a picture of in that the center portions of the thin washers are raised ever so slightly, hence the name 'step washers'. The diagram makes no mention of the flat washer in question, so I don't want to install it if it's not required.