Stihl 260 Runs then dies

Stihl 260, I was cutting and the saw acted like it was starved for fuel and quit.

I've tried:

Fresh Gas + Oil [50:1, ethanol free]
Rebuild Carb
Replace Tank Vent

If I open the tank filler cap and then close it the saw will run for longer. If I run the saw without the tank vent in the hole it will run fine. I figured replacing the tank vent would fix the problem, but it persists.

Is there something I'm missing or something else I need to check? Could the pulse line from the crankcase be jammed up and when the vacuum in the tank builds it prevents the fuel from being pumped to the carb?

Please help!

[I posted this on the Arborist website too, but I thought I'd get opinions here too]

I'm going to go check the new one now. I guess if I blow in the cap I should feel air on the other side?

I know, me too. But the one I put on is brand new. I just got back from the Stihl dealer.