I have this annoying suspension squeak and its coming from the rear..

I replaced the coils with brand new BC so I ruled that out. I lubed the swaybar bushing and that didn't work either

I notice it the most when I roll over a speedbump or driveway SLOWLY and just creep over it..

could it be the exedium racing diff collars? Any ideas/suggestions will be appreciated!

 

It could be the diff collars. It could also be any number of other things. I'd suggest putting the car on a lift, removing the coilovers, and moving each wheel up/down to see if you replicate it. It sounds like a lot of work, but it's better than chasing phantom sounds around imo.