So I figured I would see if its accurate manually. Did a few quick intervals and measured them on the saris cycleops trainer and the powermeter. Interesting finding but kind of disappointing. The powermeter seems to underread by an average of 20 watts and really 30 watts during intervals. The more interesting thing is that often at the start of an interval there is close overlap but the vector 3s drift down compared to the trainer during that interval. I guess the problem is I won't be able to differentiate if this is left right imbalance vs inaccurate reads.