[Christien]

You'll pay the full 13% HST on any vehicle purchase in Ontario. On private imports from the US, I believe they charge GST at the border and the remainder at the Ministry (for commercial/dealer imports, we pay the full HST at the border). But one way or another, you'll pay 13% tax, plus 6.1% duty if you bring it in from the states. No way around that.

RIV does indeed accept a letter from a dealer indicating no open recalls. It must be on some kind of letterhead, or have the service manager's business card photocopied on to it. You should be able to get one as part of a PPI, if you have it PPI'd at a Porsche dealership.