Just went through this in another thread.
Breather blow by
And a properly connected and functioning PCV system does not cause a vacuum leak. For that, start looking around the intake manifold flanges, carb base gasket, and any crackedl or leaking vacuum hoses, or uncapped vacuum ports. A bad brake booster or check valve can also cause a vacuum leak.
And I'm kinda baffled by your last statement, that it runs better with the PVC hooked up, and how to go about retuning the carb to run without it... WHY??