The only poly's I'm using are on the UCA's. Guess it would be easy enough to spray them down and see if that does it. No way to lube those the way they came.
Before you spray, get a helper to put their hand ON the UCA on each side while you jounce the car up and down. They will feel the noise if that's what it is. At least you will have it verified and won't be chasing a ghost.
