1993 Lexus LS 400 rattle up front

there is a rattle in the front suspension. i have had all 4 struts and mounts replaced, the rack and pinion replaced, the pins in the calipers replaced and there stillis a rattle when you go over bumps aor rough roads. the people that replaced the struts tell me everything is tight but something must be loose. the lexus dealer tells me the coil spring insulator is bad but i can't believe that would cause a rattle as heavy as that car is. appreciate if you have any ideas. Lee