My 98 has a very similar problem to yours, from the rear right side. When I go over small bumps I get a knocking noise, but over large bumps nothing. Was crawling around and smacking suspension components with my hand this morning and realized that when a grabbed the coil spring tightly the noise muffled considerably. Inspected the lower coil spring insulator and found it torn in half, so the lower coil on the spring is metal-to-metal against the coil seat. I'll be swapping it early next week to test my theory, I think it's where my noises are coming from. All else looks good and the Monroe struts are only 2-3 years old.