Manifold Heater for Cold Climates

That was back in the late 1970's, in New Jersey. At idle air/fuel flow, the fuel would absorb heat from the adapter and vaporize and cool the adapter below 32 degrees. At that point the fuel would "puddle" the engine would be running lean. After the adapter had cooled, and the fuel would no longer vaporize, the excess fuel would slug into the intake and the engine would go rich. Since the fuel was no longer vaporizing, the adapter would start to warm up, and the process would start over again. That was the cause of the surging idle.
PS: There was no change in pressure. This turbo set up was a draw thru system with the carb on the inlet of the turbo.
PPS: I stated that wrong, Yes there was a change of pressure at the carb throttle blades. But no different than a carb on a intake manifold with out a turbo.