Difficult to System Balance the Driveline
WARNING: This page is about a different car, the 2004 Pontiac Aztek and 2004 Buick Rendezvous. However, it is still accessible from the selected car via links, so may be relevant.
If after following the Vibration Analysis - Driveline table you were instructed to system balance the driveline and you experienced difficulty in doing so while CAREFULLY following the procedures indicated (the EVA strobe readings seem to keep changing), then the differential carrier assembly to which the propeller shaft is attached should be suspected to have internal problems which are being transmitted to the propeller shaft. Refer to Diagnostic Starting Point - Rear Differential Carrier in Rear Drive Axle, for internal differential carrier diagnostics.