After extended heavy rain in SoCal my car started squealing. It squeals when i turn during the whole movement, and has a strange feel and short squeal when i brake. I took the car to two recommended shops (one specialized in lexus and they both couldn't tell exactly what it was. One shop thought it may be the control arms (ball joints, possibly upper) it comes from the driver's side but places told me my car is old and really did seem to want to really narrow the prob. One shop said it looked like my lca bushing seemed to be corroding (i replaced them with oem 3 yrs ago) and the last time i had the hub off the upper ball joint seemed stiff. I did spray lithium into the upper balljoint boot and the sound seemed better for a day. Also the car will only squeal while on the ground. I've also wondered if the rack could be noisy because i added synthetic (clear) atf. What about outer tie rod end?

Any tips for further isolating this problem? Car is 1992 sc400 150k miles, struts replaced, also steering rack bushings are poly.