Easy way to tell if it's not just dirt and actual wobble on the pulleys is to take a piece of stiff cardboard or a wooden ruler and lean them against the running pulley slowly and pointing away from the direction of rotation (Don't want it launching into you!) and as you move it in... if there is a true wobble you will hear the tell tale tick-tick-tick against your test 'stick'. Old paint stirring sticks work too.

If you have a wobble, time to get those pulleys pulled and checked or see if they are just loose. As to the tensioner or idle pulley, this could be a sign of bad bearings.

This MAY be the cause of your odd idle, but I'd get the wobble taken care of first and then see if the odd idle is still there. If so, then you can begin to actually track it down without worrying that it's the wobble that's causing it.

Hope that helps...