So I have a 350 that had breathers in the valve covers, I want to install a PCV valve. How do you go about choosing the correct one? I went to the local parts store and got one that was for a 350(so I was told) I get everything hooked up and now it runs like it has a bad vacuum leak. The motor is 10:1 with a mild cam nothing special but it's not stock either. Are there hi performance valves that I should be looking for?