Can't remember what all is included in the eibach pro kit, but a common source of rear end clunking/popping after lowering is the oem sway bar endlink bushings. I'd also go through and make sure everything is still torqued properly. Something could have settled after driving a bit and needs to be retorqued.
Sent from the Death Star.
2012 Kona Blue 3.7L V6:
Borla LT headers, O/R h-pipe, Borla S-types, 3.73 gears,
Steeda adjustable UCA w/ mount, BMR LCAs, Airaid CAI,
LCA Relocation brackets, AE driveshaft, GT 80mm TB,
Black 18x9/10 2010 GT500 Wheels w/ Nitto NT555s,
Eibach Sportline Springs/shocks & Koni STR.T Struts