Has anyone used this manifold?

I would not spend the money on that manifold, if you are not doing any other mods. You will see an increase in performance, but not a lot. It is not the fault of the manifold, but the engine needs other mods to take advantage of it. If you are looking for "Bling", these manifolds show up used for under $200. If you want a new one, I have one I will sell for $220.00 plus shipping.
Just my opinion, but I would spend $300 on milling the head, first.