Ran all my pre-flight checks. IMU's were all with in acceptable ranges. Extremely light breeze hardly noticeable. Took off and i1 held its position but it seemed to have alot of play as it was holding. When I started flying forward the i1 kept veering ever so slightly to the right. It wasnt turning it was almost like it was just ever so slightly sliding to the right. This only occured while flying straight foward or straight back. To flight straight I had to apply a little left pitch (I have moved the pitch control over to the left stick.) Any ideas why this was happening?