While looking at my Hanger 9 Pulse XT's firewall straight on...I noticed that the mounting holes are not centered- but a bit off to the right. Is this normal?

Yes, it allows the prop drive washer to be centered in relation to the longitudinal axis of the fuselage (when looking down on top of the aircraft ie plan view). As the motor is pointing right when viewed as if sitting in cockpit, if the back of the motor was not off to the left hand side slightly then the propellor would not be in the centre of the cowl. Hope this helps.