FWIW, the only time I have ever seen this problem it was on a 80 Malibu and the problem, other than it being a Chevy, was a kink in the hard line part of the high pressure hose going to the steering box.

Worked fine one direction, hard to turn the other direction were the symptoms. I could never figure out why one way was fine the other not.

They say there are no such thing as a stupid question.
They say there is always the exception that proves the rule.
Don't be the exception.