Boost Leak Tester for your s4's y-pipe inlet. Comes standard with a cap for your crank case vent, 30 psi gauge, tire valve stem fitting and one stainless steel T-Bolt clamp.
Fit this over your Y-pipe, and clamp it down. The vinyl cap is used to cap the crankcase ventillation flange off the y-pipe to inhibit the test pressure from escaping through the crank case ventillation valve and into the crankcase. Use the provided zip tie to secure it.