You can add GM.IAT2 by using comma as a separator...
e.g.:
Code:
;IAT Spark Table
B5107.ROW=SAE.IAT,GM.IAT2
B5107.COL=E67.APCYL_DMA
;IAT vs RPM Spark Multiplier
B5108.ROW=SAE.RPM
B5108.COL=SAE.IAT,GM.IAT2
;IAT vs ECT Spark Multiplier
B5109.ROW=SAE.ECT
B5109.COL=SAE.IAT,GM.IAT2
when you hover your cursor over thes IAT axis of those tables, a yellow tip will popup showing you the alternate link pids...
so you can log either pid...
I'm not sure what happens if you log both, I think the first pid mentioned has precedence, if so then reverse the order of the pids shown in the example above.