Discovered Friday after initial bake cycle that the new calibration leaks (had been closed during bake) were proving to be a significant contamination source when opened, particularly the N2 bottle.  This is worrisome since the fill pressure is sub-atmospheric (500 torr) implying that it could have been opened while at atmosphere? I believe that I have been in control of these since new and would not have done this but I can't be sure as they would have been stored with various other cal-leaks until needed-hmm.  Anyway, I don't have a suitable replacement yet so I elected to rebake everything with the cal-gas valves open - Nominal 200C with exceptions such as <100C for the cal-gas valves.