You are correct wrt the tire size - 345/35-15. It's the offset of the rim. Mine are a 5.0" backspace which is pretty close to the Group IV factory rims. Not sure what your wheels are but they must have a deeper backspacing to tuck under a narrower body car. Try taking one of your rims off and position it with regard to the hub with a 5" backspace. Maybe its not 4" with your GTS flare but it will still be beyond the edge IMHO.
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