Every swap I've done we have removed the canister. Completely take it out and route a hose from the metal nipple coming out of the fire wall to below the engine bay. This hose vents excess pressure that is in the fuel tank. That is all the canister does but instead of venting to the atmosphere it sucks the excess gas back into the combustion chamber. That is why the vacuum nipple you plugged on the throttle body only shows vacuum when you press on the gas pedal and not at idle.