Catch can question

boosted mk3 supra

New Member
Authorized Seller
Sep 16, 2010
Yuba City
So I have a question, I have added a 3 port catch can and it has a breather, but I capped off the breather, also added check valves on both pre turbo and tb side and I have alot of vacuum when pulling off the oil cap, is this normal. When I out a filter on the top of the catch can the oil cap can be removed with no issues.

Just wondering if the vacuum is normal, since I added check valves to both sides of the "vacuum" source
Should i have the top of the catch can capped with vacuum in the crankcase, or with the filter with no vacuum in the crankcase?

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