The stock suspension has rubber bushings which have 'compliance' - that is, they compress under pressure. Non-compliance means the soft rubber parts have been replaced with something that does not compress, like Delrin. Sometimes even aluminum.
Less compliance in the rear cross member means less camber is needed to compensate for suspension movement, as an example of why you might want to do this.
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Don't no nuttin 'bout no NSX;
Don't no nuttin 'bout birthin' no babbies.
[This message has been edited by David (edited 10 September 2001).]