I don't mean to be blunt or dismissive, but the pressure in the veins/arteries has nothing to do with (a) the thickness/elasticity of the wall tissue, (b) the diameter of the arteries/veins, or (c) the number of (branches of) arteries/veins.
This can either be caused by a more prominent maxilla (upper jaw) or a retruded mandible (lower jaw further back than it should be). This causes a discrepancy in how all teeth contact, and can manifest as an increased overjet. An increased overjet can also be caused by a discrepancy in the number of teeth, or the length of the arch.
Carburetor's cannot account for changes in air density and that is why you need to rejet at different altitudes(air densities). The exhaust, on the other hand, does not change the air density of the air going into the carburetor.