I'm a little fuzzy when it comes to the various crankcase ventilation schemes used over the years, the only kinds I've ever seen were the dump tubes on the old B18's (simple, not EPA approved. At all.) and the orifice style, where the fitting on the intake manifold had a simple small hole.

But I'd guess that if the car runs better with the hose pulled, I'd think that perhaps the carbs are too rich. You are letting more air into the manifold past the carbs, and diluting the mixture.
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'63 PV544 rat rod, '93 Classic #1141 245 +t