Depend on how cold you are, you have to play with voltage and cold, with 2.0v I have CB (Cold Bug) at -136, with 1.9v I have CB at -154, with 1.8v I have CB at -167, with 1.7v I haven't got any Cold Bug at all. Now BFR/CFR doesn't scale a lot with too many volts/less cold. For me it was better to coole them more and lower voltage.