Dude before I bought my car it had a rebuilt motor (new pistons, brand new heads, etc.) previous owner over heated it and got it rebuilt at Kearney Mesa Subaru. When they did it they only replaced the tiny little idler pulley and the same exact thing as you posted happened to me that toothed idler failed throwing ball bearings everywhere when I was going 25mph. It just instantly failed exactly like those pictures in the other thread no warning squeal or anything. Left me with bent valves so pissed at Kearney Mesa!