thing is carl there is 6 months between those two runs.
the difference could be due to the Discharge pipe, but could just as simply between different fuels, ecu adaption from when you first had your car set to revo stage 2, or just a difference in the dyno runs on different days (atmospheirc pressure, ambient temp, granted theyahve calcs to minimise difference) plusyou can chuck your car on the dyno and get 3 consecutive readings within 3-5hp of each other.