I believe you were describing that the rear spring was rubbing on the body of the car at the rear of the spring in the coil spring tunnel? Please see attached photos. Not sure if I am using the correct terminology. When you lower the car I believe the rear axle gets moved toward the rear of the car slightly. I lowered my car 1.2" to 1.5" and my passenger side coil spring rubs also when I leave or enter my sloped driveway with curb because I have adjusted my pinion angle with adjustable lower control arm to get a lower pinion angle(Trying for between 1 and 2 degrees). I can eliminate the rubbing by increasing the pinion angle but I want to have my driveline closer to being in phase to eliminate vibration.
I also have relocation brackets, non-adjustable LCA's, and adjustable UCA from BMR. To actually solve your problem (Mine also) you will want to get adjustable LCA's. Or increase your pinion angle.
2013 GT, Track Pack
, Recaros, Kooks Axlebacks, Airaid CAI, BMR Rear Adj. LCAs, BMR Relocation Brackets
, JLT Oil Separator(s), Barton 2 Post Shifter Bracket
, Steeda Motor Mounts
, Barton Shifter
, JHR Clutch line, BMR adj. UCA and Mount, Kooks 1 3/4 headers/catted H, DSS Al Shaft
, BMR Loop
, Vogtland Sport Springs front/BMR rear, Strange Adj. Struts/Shocks, Extended ball joints, Steeda Bumpsteer Kit, Whiteline Tranny Mount Bushing, Borla Overaxles, BMR Watts, Vorshlag 3" Ducts