Briggs 19.5 hp vertical Intek won't stay running

[fo50rd]

So I got a 2011 John Deere D110 with 50 hrs on it. New fuel filter, fresh fuel, carb clean, new air filter, oil correct level, new spark plug gaped correctly. Starts up on choke when cold and then will run rough or die when taken off choke. If I pull the vent hose OFF of the oil fill tube (crankcase vent tube) that pulls vacuum from the fuel pump. .. the engine smooths out and purrs like a kitten! Plug it back in and instant stumble and die. Any Ideas? ?

 

[mechanic mark]

Post engine numbers: model xxxxxx, type xxxx, trim xx.

http://www.homedepot.com/catalog/pdfImages/fd/fd904936-46bd-471e-9536-7c3ca3698e81.pdf troubleshooting page 42