People have done the same thing with EFI Rincons. Similar symtoms- starving for fuel at high RPM high throtte.

On the Rincons there is also a filter screen inside the tank. You just pull the two screws holding on the fuel hose fitting to the tank to take it out for cleaning/inspection.

 

Good job I've been looking through the forums for a while now looking for a solution to the problem my rancher has been doing the exact same thing. When I shut it down when it starts bogging and go to restart and the fuel pump primes it sounds different than it used to. I'm going to give it a try and post my results.

 

Hope it helps but I haven't got a chance to tare the bike down yet.

 

The gas going out needs to be replaced with something. The vent also lets air in. It may just take the same time for the tank to create a vacuum as it does for it to warm up. I would look at the tank cap for not letting air in as the fuel goes out. You could let the bike warm up, then open the cap to equalize the pressure inside and out, tighten it back down and hit WOT to see if it still has full power for the same amount of time it takes for it to start acting up.