the round container you see is the fractory tool box the the tube you are talking about is a vent to releave the crank case pressure and recirulates the air back into the air intake boot alot of people will disconnect this and replce it with a small micro filter that can be bought at oreilys auto parts do not leave open drit and grimm will result in engine damage. it suggested to jet most carbs with after market pipes dealing with air/fuel and back pressure that is needed to make any motor to run.