i doubt you will, many people have ran 6.0 ported manifolds ect with good luck, the only issue was with the steed speads and i think it was because the outlet was too big
I will admit they are a nice looking piece. Not only are they nice cast piece BUT the thicker wall then piping will help hold the heat in better and should help drive the turbine harder. Not to Mention BD also took the cast manifold and ported the runners to improve velocity and evacuate the cylinders. They took the casting and improved it by porting it to get what they wanted. That tells me they wanted to get the most out of it they could.
The only thing I am not sure about is where they placed the whole for the EGT probe. And it might not be a big deal.
And like Dustin said the price is right. Well more then right to me. I would not be scared of them.
Pretty clean for a cast piece, and the price is right for anyone that is looking to ditch the 6.4 mani. But the RCD and old MPD pipes are really slick.
We sell the BD for 470 a set, makes the price hard to beat for the average customer.