they say they do custom adapter flanges. You would have to send them the gasket (of course s4 and s5 are different), and then you could run a larger internally wastegated turbo like a GT30 or a Holset HX35--assuming that their wastegates could actually control boost, which is questionable. It would be cool to try and adapt an s5 turbo manifold (which is fully divided) to a Holset HX35 off a Dodge Ram, which is divided T3 and internally wastegated.
I wish I had the money and an extra car. I wonder if you could take an s4 manifold and make a T3 adapter, and then for an external wastegate use something like this (if there's enough clearance at least):
i didnt see any manifolds just really expensive stock turbos
BNR turbos are BOLTON replacements for stock turbos, they are reworked and allow you to use your stock turbo manifold.
when you buy a new manifold, you will not be able to use the stock turbo, which means you must find and build all the components yourself to upgrade your turbo. Or you can buy a turbo kit package from major tuning companies for 2-5 grand