<b>Modification 2</b><br><br>A Turbo Air Guide (shown above) is a simple device that installs right before the turbo inlet. Diesel Power Products of Pasco, Washington makes these units for all domestic turbocharged trucks. A TAG is designed to straighten out the laminar airflow as it enters the turbo compressor wheel. The principle is simple: By aligning the flow as it enters the turbo, each passing vane of the compressor wheel is able to capture more air per rotation. In other words, by limiting air turbulence, a TAG increases turbo efficiency and allows the air to flow smoother and faster. This sounds great, but does it actually work? On the dyno the tag had no affect on horsepower whatsoever. What it did do, however, was silence our mystery vacuum cleaner.