If the PCV is plumbed properly, you need a way to get air INTO the crankcase- - - -either a vent tube into the valve cover, or a vented, filtered oil filler cap. There should be NO vacuum at the dipstick tube. Pulling a vacuum in the crankcase will result in a lot of unintended consequences. Most likely, it just took a few miles for the rope seal to wear in and swell up for a snug fit.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!