They don't do anything- the native 1377 uses the same transfer port as the 1322 (efficiency and tight engineering take second seat to keeping costs down in manufacturing). The detuned 1377 for Canada has the vented valve and a restricted transfer port (which actually works better than the native version unit in a non-detuned gun). However, people tend to believe that the "best" engineering is done by the factory, despite examples in every industry/manufacturing facility where this is not the case.

Two guns with the near-same makeup, one in .177 the other in .22- the .22 will shoot slower because the pellet weighs almost twice as much (on average). Airguns should be measured in FPE to make proper comparisons, not velocity and caliber. A QB78 puts out just under 8fpe no matter what the caliber- meaning 498fps using 14.3gr pellets, 670fps for 7.9gr pellets- assuming all other factors are equal, which is more theoretical than true as both caliber rifles only differ in respect to the bolt probe size (and of course the barrel). The problem with .177 is they typically run out of barrel (i.e. the pellet is long gone) before the propellant (Co2, air) pressure runs down, so they tend to waste more propellant and put out less velocity than one might expect using a strict fpe comparison to a .22.