Having a weird vacuum leak with a jdm engine I swapped into my speed. I pressure tested the intake and there are no leaks. I have always ran the valve cover vent disconnected and the intake port plugged. I ended up putting my finger on the valve cover breather and could feel vacuum. I could also watch the fuel trims fall from +20 back down to near 0. Reconnected the vent to the intake and boom my fuel trims are -3. Perfect. But how is this happening Iv always ran it this way. Also to note the valve cover breather is angled down like Iv never seen on a speed. I believe the engine is from a cx7. Can anyone answer why this is happening. I don’t wanna suck oil into my intake.
