Thanks, ... so someone else is interest in this.... LoL.
The Original VW manifold flange has oval passages equal to about 1 5/8 inch diameter opening to the vales but they choked off the high end performance by using small intake runners smaller in diameter than 1 3/8 inches and gave it a plenum size of over 6 litres which helps the low end torque below 2500 RPM, but above that they reply on the runner length tuning to get the midrange.
The goals have changed as I have limited resources, I'm building it more for my needs, which is to say for track use, so performance and drivability in the 4K to 6.5K is essential; and not to rev to the stratosphere like the IE version.
One key feature that I'm adapting into the design is the ability to change/vary the runner lengths very quickly. I made some measurements and assumptions; then used this calculator to determine that the runner lengths will be between 8.5 to 10 inches (the 2 inch head port to valve distance is taken into account). http://www.wallaceracing.com/runnertorquecalc.php
I can customize shorten the runner lengths to rev higher but will require the EI SRI Tune to provide the extended fuel and ignition timing way past the programmed fuel cut off, or limited by the availability or lack of availability of the maps.
One of the major challenge because i'm not using metal, is the cyclic loading from the damn thing vibrating and having an overhanging mass (moment) that contribute to cracking at the welds/joints.
EDIT: Thanks to anyone who contributed, BUT the PROJECT iS ON HOLD.
The materials I was using simply can't stand up to the chemicals (gasoline and oil) and heat. This explains why I could get pretty good results for a week but would encounter problems with cracking, creating multiple vacuum leaks shortly there after.
This is a hobby for me so, I'll continue in my free time and if/when I have something worth while I will share it with you.