I'm going to bet your rear bumpstops are falling apart or are completely missing. Get up under the car and look. Also if your car still has the SLP aluminum rear bumpstop spacers you should remove them to regain suspension travel you lost when lowering.

 

I trim my bumpstops down and I still have the spacers

 

Take the spacers out and bolt the bumpstops back on. The ride should improve.

 

I run BMR/Bilstein for about 30k miles or so. Rides fantastic. I also have SFC's. I wouldn't say it rides harsh at all. Just typical F body. It aint gonna ride like a Caddy!

 

What is take out the spacers going to do

 

I also have BMR/Bilstein setup and I think it rides awesome.

 

If your vehicle is lowered due to the springs you need to mate them to the Bilstein "B8", they are constructed and valved for lowered vehicles. If your vehicle was stock height when you installed the Bilstein shocks, you probably purchased the HD "B6".

 

Where can you buy these B8 Bilsteins for the 4th gen fbody?