One particular aircraft or all of them?
Is the vibration on one particular aircraft or all of the ones you fly?
I ask because I once flew a Caravan off of gravel strips. Naturally, every now and then, the prop needed to be dressed.
Over time I started to detect a vibration at reduced power settings when I was entering the traffic pattern.
I told the mechanics about it and they said they balanced the prop. After that the vibration lessened somewhat but still existed.
A couple days later the plane is grounded due to the fact the mechanics were using the wrong template over the blades to determine whether or not its wear was within limits.
As you may know the Caravan may be equipped with an aluminum or composite propeller--different shape--different template--different tolerances.