Aircraft: PA32R-300, GNS430W, Sandel SN3308, CenturyIII.
When I first purchased the aircraft in 2005, it had a non-WAAS GNS430 and the autopilot tracked the course well in all selected options (NAV, OMNI, HDG, etc). When I had the GNS430 upgraded to a GNS430 (2009), I started seeing...