I jsut had this on my 91 RS LWB... I thought ball joints, limiters, etc. Then I had a close look at the shocks... the bottom bushing was completely gone on one side, and barely anything left on the other.

Turns out after 20 years, 133K they were still the original Mitsu OE shocks! Replaced them with KYB's... so far so good except I did hear it again for 1 other time... just like you said, steering at the limit, usually backing down a grade, I hardly heard mine going up grade even before the shock change. my limit bumpers are in good shape, so who knows. I havent heard it again for the last 2 weeks so fingers crossed it was jsut "settling"!