The stock turbo inlet duct turns out to be a restrictive design due to it's "S"-shape path.  By giving the intake charge a straighter shot to the turbo, the engine can run much more efficiently!  Due to it's better efficiency, boost levels are higher.  Boost can climb as much as 2psi due to the better, straighter design.

You can built your own TID pipe with a section of 45 pipe.  The inlet to the stock turbo is 2-3/8" or 60mm.  The airflow meter outlet is a little larger than 3".  Getting soft hose connectors with clamps is all that's need to complete the modification.  You'll need to figure out how to plumb in the emissions fittings (one for 1986-1988 models, and two for 1989-1991 models) and the stock compressor bypass valve (i.e. stock blow-off valve), if you're planning to keep them intact.

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