IMHOWith uncut factor springs, I bet your suspension issue is your KYB GR2 strut choice and not the springs.
This is called suspension dampen {Compression and Rebound} that control the energy generated by springs.
*Compression rates depend on how quickly the shock/strut compresses the spring
High compression compresses slowly / Low compression compress quickly
*Rebound rate is how fast it returns to its original, uncompressed state
High rebound allows for a softer ride / Low rebound is for stiffer.
KYB GR2 has less dampen
KYB Excel-G has more dampen
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Original Owner of a Silver '88 GT
Under 'Production Refurbishment' @ 136k Miles