because of the crancase ventilation system and how it is designed engine vacuum is in the crankcase!! so when u remove the cap u just induced a big vacuum leak!!!
there is nothing wrong w/ the engine and it is a normal operating design and condition!!
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yes !!! that engine is a high vacuum motor and if the vacuum was low the engine would not run correctly!!
it's normal!! all newer cars are like that due to emissions regulations and design factors!!