Thanks.
There may be two and I missed something. I followed this Extruder Calibration a must - #33 by Termin8tor and assumed when I do T0 and T1 I will have to set two different values but it seems when I set it first it had effect on both extruders but I could be wrong.
This reply from M503 seems to indicate single has one value and dual has one value:
M92 X400.00 Y400.00 Z400.00 B888.89Current E667.22, BACKUP SINGLE E212.21BACKUP DUAL E667.22
Its quite confusing and also confusing is fact those two are so different.