Here's a quick lecture on why the FOX tb swap will net you more HP, I took a fluid mechanics course this year. (Air is a fluid!) You judge the effectiveness of a pipe system based on head loss, IE, how much of the input is lost at the output.
Major head loss is what occurs in the straight section of pipes and is caused by A - the friction coefficient and B - the diameter of the pipe. Minor head loss occurs when the pipe bends, turns, loops around, and how the flow is input and output of the pipe. To determine the total head loss of the pipe system, you add up the two.
To determine the Major head loss, it is generally accepted to use the Darcy Equation, which is Head Loss = (Friction Constant)*(Length of pipe / Diameter of pipe) * (velocity ft/s^2 / 2*gravity).
To determine the Minor head loss, use the derived Darcy equation MHL = (sigma of all friction coefficients) * (velocity ft/s^2 / 2*gravity).
The sigma is all of the friction coefficients added together. A friction coefficient is extremely important when the pipe sections are close together and short in length. In longer pipe sections the coeficient decreases. In a 20 inch section of pipe, they are not very important.
You can see how the larger the diameter of pipe, the smaller the major head loss would be. The longer you can sustain the largest diameter possible, the more fluid will flow more efficiently. Conversely, the slightly higher angled bend in the Fox TB will have an almost negligible negative effect.
Ultimately, you will gain more with the Fox TB.
