SS_Firehawk

mismatched tires is definitely plausable. Alignment after drop definitely also. Checking the alignment is cheaper. I woul start there first. Also if your sway bar is adjustable, set the rear to the softest setting for now to allow the body to roll a bit more if it feels like your tires are sliding, at least until you can figure out what it is. Z's should be rock solid, even at 120 mph without a spoiler.

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