Yeah, I know alot of you have experienced the same issue. In my case, I have an 01 Z51 M6, and it squeaks like crazy over bumps. No problem, I'll replace the bushings and end links. So I bought poly bushings and metal end links all around and installed them. The problem did not go away. I made sure to use a the full tube of grease that came with them, though I only lubed the inner diameter and not the outside that rests on the bracket. One thing I did not do was completely clean off all of the rust that was under the area that the bushing covered because I didn't want to reduce the size of the bar. In the case of the rear, it was rusted pretty bad so sanding it wouldn've taken off quite a bit. I am contemplating buying the C6 Z06 bars and bushings, but I don't want to spend money needlessly since aside from the squeak, I'm happy with the handling of the car (I also have Bilsteen Sports on there). My question is, can I take the bars off completely and drive the car to see if the noise goes away? If it does, then I will decide if I want to try cleaning the existing bars or purchase new ones. Also, what else could cause this? The only other thing I've found while doing research is the exhaust hanger springs, which I greased the crap out of with water proof Bell Ray grease.

Also, I would like to point out that it isn't necessarily a quick noise when the suspension moves. Sometimes it is, but a jarring jolt will cause a quick squeak, as if the effected area is vibrating (parts rubbing together quickly).

 

I should also point out that I have ruled out the targa, windows, and hatch. I definitely sounds like it is coming from underneath.

 

I disconnected the sway bar and took the car for a ride... the squeaks are still there. Maybe I'll try to get a video so you can see what I'm talking about.