You should be adjusting sensitivity, not the delay. If you're getting a bounce back effect after doing a piro, then increase your delay untill it stops. If you're getting constant hunting, lower the sensitivity untill it stops. I'd first check all your linkages and make sure everything moves absolutely freely with no binding anywhere and make sure your tail blade grips are tight to the bearings with no slop in them caused by a loose screw (can happen sometimes after a few flights if you never used a thread locker on them). Also make sure that there is no excessive vibration reaching the gyro.

If all else fails, try a faster servo on the tail.