I bought a potentially new Zenmuse Gimbal and installed it with the Anti interference board internally. As per many video online for placement and how to.
Calibrated RC and Phantom again with gimbal. And at first the X1 control for the Gimbal was smoothly working.  but when i lift the P2 off the ground and hover it goes into a weird Full tilt continuous freak out.
Also it seems harder to stabilize and hover.  It seems to always want to fly backwards meaning like pulling RIght stick down.. ever so slightly.

This doesnt  happen until it gets off the ground. once off the ground thats when it acts weird.  I am using the P2 with standrd RC with gimbal control on the back.  AFAIK everything is calibrated correctly.
  I dont want to Assume the Zenmuse is defective right off the back becasue it was CLaimed to be NEW and in perfect condition but i also Dont want to rule out DEFECT or damage.
do i need the Anti interference board?
Is there any other specific calibrations i need to do for the Zenmuse on the P2?
Do i need to consider this Defective, damaged?

This is what it does on power up it acts totally normal until it flies and  the second video is of the it does from the P2 POV.

Did you calibrate your transmitter by itself using the DJI RC system assistant? I believe you would calibrate the lever on back as well using that software, with the transmitter connected via the usb port. Then I would calibrate everything using the phantom 2 assistant. Pay attention to how the lever in the back calibrates. It should move smoothly back and forth. I had that type of transmitter, and I never could get that lever to work right. I've heard others have had the same problem. Good luck.

I saw a fix for adding shim washer to the inside of the controller to make contact with the gimbal slider an the potentiometer. ill do that and recalibrate.  

After installing new hardware I would recommend a full IMU calibration when the craft is perfectly level front to back and side to side. Then do the RC calibration and before take off calibrate the compass. If all calibrations completed and satisfactory she should fly clean and hover properly.

Also check your gains in addition to the advice you have already received here.  You have added significant weight to the P2 and you may want to dial the gains down a bit.