I am sure TWest can provide a better answer as well. If you go to his website and read the information he provides in his technical data regarding the overview of how the fueling system functions you will begin to get a better grasp of how it actually works against itself.
Toward the end ofthe technical data, he discusses the WAVES that take place. Those waves actually create a shockwave in the fuel in the rail. They create a turbulence inside the rail. The turbulence runs interference with the fuels ability to enter the injector lines. Those waves/turbulence are what you feel as pulsations above and beyond the normal pulsations created by the CP3 and it's pumping pulsations as it moves the fuel.
Before you install the modded rail, start up your truck and FEEL the injector lines, loose grip between your fingers. After you install the modded rail, repeat the feel. I bet you will feel a difference.
By boring the fuel rail you increase the area of fuel and fuel volume itself, the larger area acts toward a broader disbursement area of the waves inthe fuel volume, tames the waves of turbulence down, gives a smoother consistent entry of fuel to the lines and ultimately to the injectors - which reduces the pulse pressure so to speak and increases the longevity of the injectors life - less pulse wear.
Now my iteration of how this all works is crude, un-technical, but it is certainly close enough to the truth in a way of my understanding it to make the addition of the modded rail a benefit.
From what little I have read, the mild rail is what Mobius1 describes, a center bore of the main rail. The wild rail has everything bored out, think porting as a descriptor of additional benefits over the mild rail.
Ithink that driving manners would see a benefit the most in the bottom end power curve, or at least that's where I would think it would be,although it should also contribute to the power curve in the overall but probably less detectable as the curve rises and in it's duration effects as power increases.
Someone who has done a dyno, a before with the stock rail, and an after with the modded rail would probably easily confirm my speculation regarding the power curve.
I have plans to upgrade my turbo with a better towing related turbo, probably a towing cam somewhere in the cards as well. When I install the WILd rail, I will also be installing a GDP intake plenum. The GDP plenum will be the last piece of my intake mods to complete a total intake package (if you will). I have improved my entire intake air system at that point. My goal now is to improve my entire fueling system. A modded CP3 or the addition of the 'bag of parts' is shortly to follow the rail mod. If I need more fuel volume/pressure over the stock 10psi I have now, I will be adding an AD150. I already have the AD150 and was planning to install it when the stock lift pump gives up the ghost - and we all know it will someday.
CD