Questions for TacoChief re headers

I saw on another thread where you said you work for Toyota and put headers on your Taco. I have a '00 4wd with a 2.7 with two cats (I think that makes it an LEV engine?). The exhaust manifold looks like a shorty header anyway, made of welded tubes rather than cast iron, so I am wondering whether headers on my truck will give me any appreciable performance gains. In an effort to gain a bit of mpg, I have installed an AFE Stage 2 cold air intake and a magnaflow cat-back exhaust. I have been thinking about installing Pacesetter headers and high-flow cats. I just need to make sure it will still pass Pennsylvania emmissions inspections. Any thoughts?