Serpentine Belt Tensioner & Pulley...Question

[DBBAMXLT]

Recently replaced serpentine belt, tensioner, & idler pulley on my 2002 Explorer 4.0. Belt & tensioner are Motorcraft parts, pulley is FourSeasons.
Fired up engine after replacement, all looked good. Tensioner wasn't moving and alignment mark was perfectly centered.
Now after driving it for a few days and checking again, I noticed at idle the tensioner moving rapidly just a bit side to side after I turned on AC.
And idler pulley looks like it may have a slight wobble. I installed it using original hardware (Bolt, washer, spacer, and that small plastic thing (not sure what it is) torqued to 35lbs..
Any suggestions? Comments? Help?
Appreciate it!

 

[HazyMage6]

Make sure the bolts are still tight. If so, don’t worry about it unless it starts making noise. The purpose of an automatic tensioner is to keep tension on the belt. You’ll notice it go up and down a little when you put a load on it.

 

[410Fortune]

Okay so I’ll ask
Why did you replace these parts? Was there a previous issue?

While belt was off did you spin / test all other pulleys for looseness / noises?

 

[donalds]

a VERY small amount of wobble is normal
35' lbs is the specification but that's too tight in my opinion no need to loosen it now though