I would check the idler arm. This is what holds up the right side of the linkage and keeps everything parallel. I had a bad idler arm years ago in an old Valiant, and while the driver side tire responded to steering input, the right tire had a mind of it's own. In turns it seemed okay, but going straight on the highway the right tire would randomly wobble left or right making it a real bear to handle. And it is specifically in the steering linkage on the passenger side where the noise seems to be originating.
