Pressure testing the intake system on a turbocharged car is the best way to check for leaks. Any leak in the intake system can negatively impact the efficiency of the system. A leak after the MAF can also cause drivability and running issues. Pressurized leaks may not be apparent in vacuum testing, and may appear sealed when not pressurized. Post MAF leaks are generally noted by a rich running condition on boost.
Depending on the type of vehicle, there may be common leak areas that need more attention. This is true on applications such as the turbocharged M50 based motors.
Other common leak points are the silicone couplers and the turbocharger compressor housing. To ensure that the couplers hold right, verify that the hose clamps are on square to the tube as well as sufficiently tight. We recommend only T-bolt clamps for intercooler piping, but screw-type can work fine for compressor inlets. The compressor housing on a turbo can be sealed to the center section in various ways. Some use a paper gasket, some use a rubber o-ring, and others use nothing. Some that ship with nothing or with a paper gasket can benefit from switching to an o-ring. Most compressor covers use a 5.5 inch ID o-ring like this.