score:6
Your best source of information on this is the airline, who wouldn't sell you the ticket if they thought you couldn't make the connection. But some extra information to reassure you:
If you stay airside with no need to clear customs or security, and your first flight is on time, you will probably spend 90 minutes sitting at the gate wondering if you should go shopping in the terminal. And even if you need 30 min for security, 30 min for customs (both estimates are probably double or triple what you really need) and your flight is 30 min late, you'll still make it.
(I've never changed planes in YYZ. But I have landed there from international flights, and left from there for international flights, many many times.)