Here’s the link to the test results for the 3X2 dyno test.

http://www.y-blocksforever.com/forums/Topic40554-3-1.aspx 

The 553 and 573 intake dyno results are very close to each other with the 573 intake being the better of the two.  While it’s probable that porting the 553 intake will bring up its horsepower numbers up so that they equal those of the 573 intake, testing this scenario is actually the only way to know for sure.  I’ve now done enough intake porting that you have to be cautious in removing material in the manifolds simply due to the results sometimes going backwards instead of actually improving.  Instead of actually match porting the intake to the heads, results are better in some instances where only the ‘inside’ edge of the intake port is port matched to the head while the ‘outside’ edge of the port is left intentionally alone with a step remaining between the intake and the head.  A full port match can cost some lowend torque without any improvement to the top end horsepower numbers.