This test is of a Project:B5 modified RS4 intake manifold.  The IM uses a stock RS4 size throttle body inlet, enlarged plenum, and has porting/cleanup done to the interior of the plenum and runners.

This intake manifold is shown below:

Project:B5 IM Flow Test Results:

Results for this intake manifold, labeled RS4 Mod/76, compared to previously tested manifolds are shown below.

The results with all of the IM runners open are substantially higher than a stock RS4 intake manifold.  I am doubtful the enlarged plenum contributed much to the significant gains given the low pressure, static, nature of this test.  That leaves the porting and cleanup, which appear to have helped quite a bit.

Surprisingly the Project:B5 IM outflowed the other modified RS4 IM (RS4 Modified/80TB) by a decent amount.  Anywhere from 8%-12% additional flow was recorded with the Project:B5 IM versus the 80mm TB equipped RS4 IM previously tested.  (The additional flow is not likely a result of day-to-day or test procedure variations.  As much as a 3-4 CFM difference (2%-3%) would not be unrealistic if testing the same part on different days).

My theory for why this IM outflowed the more modified 80TB IM is this.  With a single runner open the size of the IM inlet where the TB attaches is less important, the more restrictive area along the airflow path is at the runner, making that area, and any modification to it, more important.  The type and quality of porting or cleanup are the only other obvious reasons for a difference occurring, and from these tests it appears the Project:B5 IM had something done that contributes to it outflowing a similarly modified RS4 intake manifold.