I was running full polyurethane setup for my rear suspension and it was "squeaking" quite a bit went going over speed bump. To stop the squeaking ('Rubber' rubbing against metal), I decided to spray the polyurethane area with silicone grease; BAD IDEA! The squeaking got worse. Even traveling on relative flat road, the rear suspension was squeaking like crazy.
Essentially what happened was that I got rid of the grease that was present was the silicone grease, therefore the squeaking got worse.
If you are still running original rubber inserts, use the red rubber grease.
For polyurethane, I used Energy Suspension Formula 5 Prelub which came with my Energy Suspension kit.
In my case, I had to take the suspension setup apart to applied to areas where the polyurethane/rubber meets the metal.
No more irritating squeaks!
So if you are installing polyurethane or replacing rubber inserts, do apply the required grease.