Were all the little bearings replaced/reinstalled in the blade grip.... Are the dampeners ok... from inside to out, there should be a bearing, spacer, then another bearing, then a washer. Are the blade grips tightened too much? by drifts is it only to one side? or is back and forth....
If it is only to one side you need to "trim" your tail... DO NOT DO THIS ON THE REMOTE... you have to do this per the instruction on the flybarless... assuming it is flybarless.
If it is going back and forth either your gain is wrong or something in the linkage is to tight, that linkage should be as smooth as butter to move.
If it is a MEMS gyro make sure that you have it on the right setting... i.e. standard vs digital..
Also ensure that your tail is 90 degree to the main blades and not tilted, that will cause drift as well....