Just disconnect and plug the lines that go to it. I wouldn't bother though, all that does is burn off tank vapor and crankcase fumes. If you disconnect it your car will just pollute the environment more and you won't gain any HP. The purge valve on the canister will not open when vacuum is low, only when it is high, the better to suck in the fumes. When you are accelerating vacuum drops almost to zero at WOT, therefore the thing won't open and there is no performance loss.