Had the noise since I got the car, 23K or so ago. It hasn't got any worse, unless the car was loaded down, or until I shimmed it up yesterday.
The motor mounts are not giving any sign of being bad, but I'm sure they are tired. I might replace them before mucking with the csb, the trans mount I put in 23K ago as well. I had hoped the rear suspension re-fresh would raise the rear up, which it did, and get rid of the thump since it was much worse with the rear loaded down. No luck though. And also the rear bushings were replaced, so in theory the pinion angle is what it should be. That isn't really adjustable on these cars is it? I'm assuming that is the root of the thumping.