Yes a larger/more optimized TB would definitely improve your top end.

I know Loco has a race header, but it was a totally different person. I went and digged up the thread for ya:
http://www.teamfocaljet.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=2&t=008460

Here is the quote:
"Actually, you are not the first to do this. There is a Contour at the shop I have some of my work done that has had the FocusSport race header for about a year now. He went as far as to get the FOCUS bulkhead and oil pan just to have it clear correctly. At the moment He is in the process of putting a turbo on it using the JBA header similar to what Alamo did with their Focus."

-Giovanni One turbocharger. Two intercoolers. All love.