They do bolt right up to the stock up-pipes. You still have to take everything loose(just like swapping a turbocharger.) If anyone has any real interest, take the cab off. It took me and my wife around 8hrs nonstop to put them on. Cab off would have been around 2hrs for us. I am sure there are manufacturing difference because the collectors were aimed just a tad more towards the front of the truck than the stock manifolds. Not enough to cause any trouble, just pointing that out.
I never did get to do a before and after test as these were put on a couple days before it got live tuned. All I could tell was the lowend response went up(75% or so of the gogo intake per the butt dyno.) Wot egt's went down around 140* roughly. Cruising was still the same(around 650-750.) Seems that's where the pmax ran no matter what. Also I lost about 2psi of boost at wot, but the truck felt stronger(I guess more volume than pressure doing the work.)
To be honest, I don't regret them one bit, but for the average joe who will never get past the tuner/intake/exhaust stage, they are not needed. I feel the same about the gogo intake. That's a couple thousand dollars and a lot of work for at best 70hp and a couple hundred lower egt's at wot.