by capping off the throttle bodies and blowing air into a small hose that is continuous with all the turbo,intercooler,vacuum,etc. hoses. While some air escapes from the open intake valves, it still can help diagnose intake hose leaks. If you need it explained a little clearer call Greg at 818 424-6396 and I think he could tell you how to do the test in more consise terms. Good luck. Mark