Having recently gone thru a similar experience with my Raptor 30 check the following:

Tail rotor control linkage needs to be ultra smooth with no drag - check ball links as some may be too tight. The tail control rod guides may be out of alignment as well. You might need a bit more negative gain programmed into your Gyro thru the radio.
Did you use the CSM supplied mounting tape or something else as sometimes mounting tape can make a huge difference.