[AZKen]

Take that feakin air cleaner off so it gets more air and so you can see that the choke is open. See if there is any rev difference. Better or worse.
If no change then use your hand as a partial choke, or the choke lever, in various amounts of close-off and see if anything changes.
If none of that produces, get a spray bottle of gas and, between mist and squirt, it down the carb throat with one hand and throttle it to see if you can maintain that rev up.