14 YZ250F w GYTR head pumping out oil on startup

I built an engine for a gentleman that had a GYTR head installed prior. Ever since the head was installed it would pump a lot of oil out of the breather tube when first fired. Like a cup of oil. I rebuilt the entire engine. 16 crank, piston etc. I assumed it was a head gasket issue but now Im pointing toward the head since it is doing the same thing. Under the valve cover you can see that the valve cover gasket seals off the area where the breather tube meets up. Its like it holds oil up there and doesn't drain back down to the crank case. Even weirder is that I can only blow through the tube at certain parts of the stroke. Before I tear back into it I though I would see if the fine folks of Vital would have experienced anything like this.Ok everyone, GO!