Related question...

What's the procedure when flying out of YVR and connecting to USA via YYZ on AC?

As a US citizen, would I have to go through Customs at YVR first, or is the departure considered "domestic" and the actual transborder from YYZ to the USA at T2 is the only Customs and Immigration point?

I suppose there is no such thing as being pre-cleared in YVR. The long line reputation at Pearson isn't something to look forward to with a tight 1hr connection on top of any possible delays getting into Toronto.

Also, can I get receipts for the GST refund stamped in YVR or do I have to wait until YYZ?

Thank you.