I cant remember off the top of my head which wire does what.

I wired in the tech plug though and just bridged the correct pins out to flash the codes

I know for sure that a cavalier and calibra both had tank vent valves, judging on what you said by PM yours has got one, It should be attached to the 2 studs of the inlet manifold (master cylinder side)

Got any brake cleaner, if so have a good spray about !

James