The only reason I didnt address the snorkel mast was because I was considering the normal surface ventilation lineup, exhausting through the muffler. I considered the fact they were probably bringing air in through the control room hatch or the main induction, like most boats do in open ocean
Those Romeo boats are so hacked up and back-engineered by the Chinese I doubt that they even resemble the Soviet era boats. Ship alterations were probably made that affected every system, and weapons modifications probably were made that caused more problems on top of it.
I definitely always did notice that 4" vacuum. Especially when my sinus cavity involuntarily drained dramatically. I am sure you guys know that feeling very well!