Almost impossible to strip a pitman arm on anything not used off road. However, if the idler arm, tie rod, or the center link is junk. It will make everything sloppy and bind. The VAS was acting up on me in the green car once and a while. Bill C said his 6 speed fleetwood did the same thing. He can shed more light on that issue, but it looks like a Caprice steering pump will get rid of the problem forever, or just disconnect the wire harness to the stock pump. This should keep it in easy assist without firming up at speed.
2014 Chevrolet Silverado LTZ Z71 5.3 Aluminum V8 (My daily)
2007 Pontiac G6 VL 2.4 I4 (Wife's Daily)