The Arrow header has a baffle, that is about 4-5 inches long, mounted to the walls of the collector tube. It is less restrictive than the stock precat/baffle, but still a restriction. And more so than the modified versions of the stock header. It is about 1/8 to 3/16 of an inch thick, and reduces the collector inside diameter.
It looked hard to remove, but possible.
SOME of the Zard headers have a similar baffle as well.