is it worth doing air tight drywall methods and also using a vapor barrier. I live in northern canada and for code we have to use a 6mil vapor barrier. I have used all 6 mil vapor barrier on the ceilings and am using membrain on all walls that have 1.5" polyiso on the outside. The outside has 2 layers of tyvek taped and the stucco contractor installed 2 layers of 15lb felt over the polyiso before doing their wire so i doubt the wall will dry to the outside at all.

tjetson - which province do you live in?

The Alberta code and therefore quite likely the UBC does not require 6 mil per se.
ABC 9.25.4.2 and particularly sentence 6) "Where a coating is applied to gypsum ••••

IMO, it is important to have air barriers on both sides of a wall. You don't want air moving through the wall, but you also don't want air moving in and then back out of the wall, moving heat and possibly dumping moisture in the process.

If I understand you correctly, you are asking about air tight drywall, which would be a third air barrier. That seems excessive.

im in manitoba, We install 1.5" of foam over houses alot and use 2x6 walls with r22 insulation witch i have learned is wrong. Thats why Im using membrain on walls containing the foam on the exterior and just normal 6 mil over the walls that dont have the foam (garage) and ceilings