suspension clunk/pop that I just can't track down

[Dustbunnie]

I have a suspension clunking sound coming from both sides of the rear. My chassis has 200k miles on it, I have D2 coilovers and subframe spacers (the plasticy kind, not metal). This noise has been there pretty much since I installed the coilovers, but is much worse lately. I thought the subframe spacers would fix it possibly, but they didn't change it one bit.

Does anyone have any possible places I could start looking towards? I jacked the car up, and with the wheel off, jacked up the lower control arm. It makes about 2 clunks for a complete compression of the suspension, and then one coming back down. I can't see any component jumping around or see anything at all when it makes the noise, and nothing seems to have any give when I just pull back and forth..I really don't know where it could be coming from. Any ideas?