Velocity (speed) has nothing to do with pressure...however the faster the air entering a cylinder the faster the cylinder FILLS UP.."Pressurizes".
WHAT THE throttle body spacers do is the LIKE WHAT STEPHEN SAID...IT INCREASES THE VELOCITY and yes , Creates turbulence...which is WAY more Dense than smooth laminar flow..yes like a tornado!!! which Compresses the air a lot more...creating ..WELL PRESSURE!!!
spacers are the fuel injection equivalent of Velocity Stacks found in race cars using CARBURATORS.. ( its the long chrome necks.)
and yes they really work. performance throttle bodys...already come with them,