Well it all depends... first how do you have your hover set up? Some guys like to run the same pitch curve for both normal and idle-up.. for example, -9 low, 0 mid, +9 high... I myself like to run -4, +5.5, +9 in normal, and -9,0,+9 in idle up... This means there is a "transition" of pitch when the idle-up switch is thrown... Those of us that run this kind of setup know that you just bump the throttle/collective up a tad right as you make the switch... Then it's almost seemless... With matching curves, you usually have to lower the throttle/collective a bit to maintain the same point. (since the head speed increases generating more lift for the same pitch)...

As for your yawing... You have one of two things happening... First question you have to ask is rather it's a Heading Hold gyro or not? If it's a standard rate gyro, then you will NEED to add "revo mix" to your programming... As you increase speed on the head, your increasing throttle, which increases torque... That makes the bird want to yaw.... Revo mix compensates with the tail rotor.... If you have a heading hold gyro, then you need to make SURE your revo mix is turned OFF... The gyro automatically locks onto a heading without input to the tail.. Even if torque changes, it stays the same... With revo mix though, it will feed input into the tail which the gyro figures is you wanting to yaw the ship... It complies...