Umm.....You don't get a "header" for a 1.8T since it's turbo charged. What you're looking for is a downpipe and a new turbo manifold (or exhaust manifold). There are ton's of people that make downpipes, I have a techtonics tuning one myself. As for a turbo manifold, the only one I know of is made by APR, and you can only get it with their Stage 3 kit.
I agree about the downpipe upgrade; it not only increases power, but usually extends turbo life as well by reducing backpressure on the turbocharger. As for the exhaust manifold, the only other example that I have seen other than the APR is an Extrude-Honed stock manifold offered by Neuspeed. But at $700, I would put that money towards the APR stage III system rather than the manifold itself (IMO).