Here you can take a look at the new Carbon Fiber 90 degree intake. Many times when you are flying along and go to knife edge or inverted you hear a weird burble from your engine. What is really happening is you are getting high and low pressures inside of the cowl. The carb on a gas engine is run by negative crankcase pressure.The hole in the front of the carb on the carb pump cover regulates how fast or slow the pump works.

When different pressures are inside your cowl this pump gets fooled and sometimes lags or speeds up prematurely. When you use this 90 degree stack you have the same pressure in the pump as is in the venture (carb opening). Therefore alleviating the surging of your engine. Or, possibly quitting at a most inopportune time.