I got a new Freya (bought from someone that never finished it) and I am having a tail wag issue.
Some background first...
Heli came partially built, ie: main frame and engine was built, I put the tail and head (partially assembled) together, and installed my electronics.

All linkages are fine, gyro is the 601 with it's dedicated 9251 i think servo,(which I also got slightly used) and I have setup the rest fine. My other helis fly fine with no issues, I am not a newbie in this.

I hovered it and it feels great, the only thing is that there is a constant tail wag which will not go away no matter where I set the gain. In the beginning I thought I had the gyro setup wrong as I only have experience with the 401 so far. I checked however my settings with someone on the field with the same heli and a 611 (similar) and we have it at almost the same.

The wag increases with increasing rpms also. I think I might be getting some kind of vibration maybe but can't really notice anything. My blades are tracking perfect, sensor seems mounted good, tail and main shaft look fine, I just don't know what else to look for. I am just looking for some hints before I decide to start taking things apart.

There is a metal plate 1x1 inch that came with the gyro and have the sensor mounted on the heli using it, by putting sensor-foam-plate-foam and finally attaching it to the heli frame. I don't know if that metal plate causes any interference but wouldn't think so...
I am planning to check the balance of the tail blades(didn't check before, I used carbon) and possibly the tail shaft, although it really looks straight.

Linkage is smooth, sensor mounted properly, tracking is fine, and from what I see, the engine runs smooth, no obvious vibration.

Also to add, there is really no indication of vibration other than the left to right tail wag which is proportional to the rpms. So I can't say for sure it is from vibration. Maybe a bad gyro, who knows. I will attempt to mount a 401 just for the heck of it just to eliminate that possibility.

So please, any thoughts on the matter would be appreciated.