Race predictor, HRM & Race predictor seem off

Had my 955 for a week now, having upgraded from a 745. My race prediction times have all blown out, and my V02 has increased for the first time to 55. Surely this cant be right. I've also noticed that my general average HR on easy runs is seemingly lower than what was recorded on my 745. Surely the 955 has a better HR sensor and generally better accuracy than my older 745..?