After an e-mail from another forum member. It seemed the best two options were : 1) Leave the 3rd hose in place and plug it. or 2) Extend the 3rd hose up under the Speedo and put a small air filter on it.
Trying all three lines together and venting just didn't sound like a good idea.
Today I vented the two fuel tank lines together and ran the line down to the skid plate area. On the 3rd vacuum line I took option 1 and plugged it in place.
Took a hour ride today. The bike ran great. It seemed to run better now than when the canister was in place, but it could have been the nice 34 degree air temp. and I haven't ridden for a month. Seems to be working fine with this method.
2011 Adv 990R
KTM 500 exc
Sherco 290 ST