 To install the DFC90 A/P (which is a slide-in replacement for the 55X) the PFD has to be upgraded to WAAS standard.With the introduction of the IFD navigators product range (IFD440/540/550) Entegra 8.x was not dependent of Garmin navigators anymore.The IFD440 COM/GPS/WAAS Navcoms are direct slide in replacements for the GNS430W navigators.