The left one is the idler with the jrsc kit. Good luck getting a hold of a new one. The right one is the stock idler which you can get a new one from any auto parts store.
I had the same problem. Replaced the tensioner and belt and it took care of it.
FocusXtreme - Hatch Nation #96
04 ZX3 5.0, T5, 4 lug 7.5 w/ 3.73s [3/13 ROTM] ["Best Non-SVT" FITF '12]
12 SE Hatch Sport & Winter Package, ST Front End
91 Ranger XLT 3/4 drop
89 Bronco II XLT Well the body is still stock, what's left of it
97 Mountaineer 5.0, AWD, 3.73s