Confused by stock vaccum lines

ZenProtege

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Mazda Protege Titanium 03.5
I was making a SRI for my car last weekend and I noticed a vaccum line that went from the intake manifold to air intake. It seems to me like this would constantly leak boost back into your air intake equaling a large loss of power
Any opinions, does anybody know if it can be capped off? I borrowed a pic of you engine bay blkzoomzoom

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That's not a vaccuum line. I believe its a line from your PCV valve to the intake, oil blow by i think its called, people get oil catch cans to attatch to this also. Also I have seen a lil filter looking thing attached to it.

Also anyone feel free to correct me if I am wrong!
 
that isnt a vacuum line i think it is part or emissions. that is the line you hook an oil catch can to. not exactly sure what it is called. but it recirculates air back through the intake
 
it's the fresh air side of your PCV,if your not worried about smog,you can run a small filter on it,but the system was designed to be run into the intake,to reduce hydrocarbons(raw fuel),along with remove positive pressure from the crankcase.DO NOT CAP IT.that would be an easy way to mess up your engine bay.

it will push you dip stick out,and spray oil when you boost.
 
thats a weird looking pcv valve or I guess i'm used to the obvious looking plastic ones on most cars....I pulled the line off to see if there was any sucking and there wasn't, I just assumed it was a vacuum line by looking at the nipple it attaches to
 
wrong side,if you pull the cover off the engine,you will see the PCV.there are 2 hoses to a PCV system,one has the valve,the other is the breather.
 
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