Weather Corrections

[Bruce Plecan]

OK, we have on some applications, Baro, and IAT/MAT.  During
crank, we can sample for airtemp, and Baro.  As I recall there is
a formula for working out humidity from that.  Is that "correction"
used somewhere, in the gm ecms?.  They have some tables for
baro, and temp, so would it be safe to assume that the humidity
is worked into the corrections somewhere?.
  Is there enough change in MAP when changing exhausts that
the Baro/MAP/Vac correction accounts for change in backpressure?.  Or should
the EGR flow, be adjusted for that.
If it should then does the timing/fuel corrections for EGR need to be
changed ?.
Thanks
Bruce