just install new XRX. first flight. NW bound at 6,500, with FF. I detected A/C same direction -2,200 less than 3NM at my 5:00. then it quickly became -1,200, then went to my 7:00 then quickly back and forth between 5 and 7. then instantly to -200 at a stable 5:00. I deviated my track to avoid. Asked ATC if they could see. they did not. Help please!!

The first thing you need to do is recalibrate the compass in the XRX, as well as the altimeter. Compass accuracy effects where the traffic is located direction wise, the altimeter effects what traffic you see.
A non-calibrated compass will show targets exactly as you described, either in the opposite location or bouncing back and forth.
If the altimeter in not properly set to match pressure altitude, it will distort your view of traffic showing traffic you can't see, or even showing your own plane as traffic.

Directions for calibrating the compass and altimeter are in the owners manual starting on page 43.
If you need assistance please call our tech support line, we can walk you through the procedure.