excessive 340 crankcase pressure

It looks like the OP has 2 PCV's tee-ing together, then to the catch can, and then back to the carb's PCV port. If that is the case, it will indeed absolutely draw a vacuum in the crankcase with 2 PCV's; you don't need airflow in create a lower pressure in any closed chamber. (The inflow of air is actually going to be from the blowby... not a good source for keeping the crankcase clean, but a source nontheless.)

Regardless of whether the OP has a breather or not, at high RPM's, there will be the most blowby and the least flow into the PCV port on the carb as there is almost no vacuum there at WOT, regardless of the number of PCV's or the type. In that case, adding a breather may help as it will reverse flow at WOT and become a fairly open vent for the crankcase pressure. At least the dipstick may not blow out oil.

OP, when you say there is oil mist out of the dipstick tube, is that at idle? Or are you just seeing the results after WOT operation?

And, I can't read the label on the hose connected to the PCV's valves but if it is fuel line, using that is a no-no. Proper PCV hose will not collapse inward under the vacuum pressures in the hose; fuel line can collapse.