fabracated valve covers and header evap

You may want to find that out. Maybe call the supplier or something. You can get ones that open with less or more signal. It all depends on what you're doing and how far you want to look. You will also want to make sure the stamp-out in the base of the breather is open far enough, and it couldn't hurt to do a leakdown on the motor too - just to be sure it's nothing internal.