According to Speciality Zed "The GT30 series turbos have boost creep issues with the dividers installed, we have tested multiple set ups with and without the divider and found no change in spool up or overall power with or without the divider. So we make the GT30 series downpipes without dividers and this makes sure they do not have boost creep issues.
We use a 1.5" wastegate pipe, but the area available with the door part open does not allow enough exhaust to get around the turbine wheel to control boost at high RPM with the divider installed. This still keep more than half the circle area available a direct flow to the same size opening that expanding and drawing the exhaust gas in a controlled way. Huge gains over a large open downpipes that causes turbulence.
and
The normal 5 bolt Garrett turbos have a 2" starting outlet for the turbine wheel, we make the standard downpipes match the 2" outlet and bump to 2.25" for the first bend. The 3071 and 3076 that are used with T25 .64 housings have the gasket area cut open for the larger turbine wheels for those turbos. We make custom flanges for those turbo and start the pipe size at 2.25" to match the housing of those turbos. The rest of the downpipe is the same.
Wont fit what I am doing with the silver Zed so my loss is your gain
Wont give them away, but feel free to make an offer, I can just laugh. Or just be nice and pay the US$650 I did and save the freight.