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It seems that at some level of increased performance, the original PCV valve spec does not flow enough air to relieve the crankcase of pressure. Mostly noticeable with any forced induction engine, but certainly a possibility on naturally aspirated ones too. Symptoms of insufficient PCV flow are obvious, usually leaks in numerous places and oil mist if you have open breathers.

One example I have is my old '79 Bronco which has an EFI retrofitted 400 engine. Originally, these engines didn't produce much power, possibly around 150 hp tops LOL. After I went through it, it's a solid 350 hp, 450 ft-lb engine and the stock PCV wasn't cutting it. I was leaking out of the oil pan gaskets, valve covers, every orifice you could imagine. I revised my PCV plumbing using 5/8" ID tubing (fully sealed breathers due to EFI) and not kidding, the engine stopped leaking completely. Bone dry. Runs extremely efficiently and makes power everywhere, probably because the ring seal is greatly improved.

If the Wagner dual valve assembly is what it says it is, it certainly couldn't hurt!
 

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I should mention that I've had some good luck with the PCV valve for a 2003 Mustang Cobra that was equipped with a large positive displacement supercharger from the factory. The valve is identical dimensionally to the stock late model 5.0L PCV valve, but flows significantly more air. Motorcraft EV153.
 

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A properly functioning PCV is a joyous achievement - mainly due to the lack of oil leaks and how much crisper and cleaner the engine performs throughout the operating range.
 
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