Are your Jam nuts tight? That can make noise as well in some cases. Just a thought.

 

I checked them last time I was under there which was on Wednesday. I'll check again, but I don't think loose jam nuts would make this noise

 

Ok, just checking.

 

Let's review what's been done (I'm going back to the original poster's issue).

Setting aside shocks for now. You added a stiffer front springs, that also lower the CG and roll center of the car. The rear of the car was also made stiffer, and the rates themselves aren't a bad match to the Pro-kit fronts. However, you rear roll center is higher than the front is, which in itself will make the rear want to dance more.

Then you added a 21mm bar in conjunction with your 32. Folks do this all the time, and it's a mistake. Unfortunately it's more internet propaganda. a 32/21 was only a 1LE setup for 1 year, and in order to use the 21 rear bar, GM also used STOCK rear springs, not stiffer 1LE springs. Note that all 94+ 1LE's use stiffer springs, but a stock 19mm rear bar. So combining your spring rates with the bars you run, you have a car that is stiffer in the rear relative to the front than a 1LE ever was. That will make the rear have less grip and dance more.

And then you added poly rear control arm bushings. Unlike many folks who spout how terrible they are, I don't think so *IF* you setup the other things accounting for them. See, they don't flex like rubber bushings or rod-ends, which doesn't let the axle articulate like it would before. In other words they add roll stiffness, much like more spring and bigger bars. To put it bluntly, the rear of the car is too stiff vs. the front.

On to the shocks. SLP's rear shocks are nothing more than standard Bilstein HD's. I feel that they are too soft, even with stock springs which is why we rarely use a 4th gen HD on the back of any Camaro, 3rd or 4th gen. Consider that a shock is a spring damper. You added more spring in the form of the SLP unit, and you also took away some travel for the shock to do it's damping in since the car is now a bit lower. I do not believe your rear shocks are optimum, but are also not the biggest issue (see above).

As for the front shocks. SLP Eibach's are not a great match for most things, but really not for Pro-kits. First thing SLP has done is take AWAY compression damping from a standard HD (it compresses more easily). You upped your spring rate, but not enough to take away that damping. The result, the front wheels yeild a bit more easily than they should, further lowering the roll center and center of gravity, and also in some circumstances letting the car contact the bumpstops really hard and suddenly. Hitting them isn't an issue controlled. Then you have a spring that is 400 pounds and this is where the real fun begins: The SLP springs go as stiff as 450 and are valved for that, which believe it or not results in what's known as "packing". Soft bump allows the spring to compress faster/a little further than it would with more bump, and the greater rebound doesn't let the spring extend fully/as fast as it should which results in less compliance from the front of the car. As you may know, I Revalve shocks as well. And I can tell you for Pro-kit's I run more bump than SLP does, more low-speed rebound to enhance response, and more high-speed rebound vs. HD's, but usually a little less than SLP does to avoid that problem.

Would a bigger front bar help? Yes, because it would keep more weight on the inside rear wheel when cornering, which means the outside rear is carrying less of the load and has more "reserve" traction. Also a bigger front bar would help balance the out of whack roll stiffness front to rear.

I'd recommend a bigger front bar, and removing the 21mm bar in favor of a 19mm bar to start. From there we'll get a better idea what we need to do after that, if anything.