Its not about the air being rammed into the engine. The intake plenums are setup so the air comming in is tuned. Wether it is a trumpet or "velocity stack". The two really have the same effect. If you think about the air being drawn into the plenum on the velocity stack, the air will hit the end of the barrel and get sucked in on the short end of the taper. The reason the taper is there is to deter from a vacuum effect. If air was blowing over the tube end, without that slat, the air would be sucked out of the carb. Fighting the intake charge. Now if you spun the taper on the velocity stack around so the tall part of the stack was forward, a siphon effect would be happening. Low performance. Most are better off leaving the trumpet on there because 360 degrees of comming in is air is better than having 180. If the "velocity stack" was mounted in the cowl one may have better results. But neither one will have a ram air effect. Hope this helps.
Adam