Noticed one side of my runner sits about an inch lower than the other in the rear. Not really the notorius rearend sag since it still is 2 inches higher than the front. Also noticed that the springs have a gold rubber coating on them. Any idea on who makes them?, replace both?, replace one?. I like the way it sits and rides and don't care for a stiffer spring, I just want it to be more level across the back. Maybe I'm just too picky, ideas??