If you have lifted the ride height then the shocks will be over extending, try lowering it back to the factory setting.
I'd look at the condition of the rear crossmemeber inside the rear isolation bushes, body corrosion will make any crashing sound worse oddly enough, also check the condition of the rear floor above the under-floor crossmembers. Yours will have the chassis brackets welded on (the earlier ones were bolted and adjustable), make sure they are still hard up against the crossmember or the floor will not be supported.
If you've got loads of camping gear I'd strongly suggest you check your axle loading, the LSE can weigh slightly more than the 100 inch using the same componenets so you have a slight margin of error but be careful you don't go too far.
The EAS is definitely best using the factory settings, if it gets stuck in High it will raise up to the top of the shock, evening out ground pressurer to restore grip if you are cross-axled, but the ride quality is shocking (pardon the pun).
Unless you fit
longer air bags that is ;)