Got some on the way. The diesel is an internal combustion engine, and any time you can ease the breathing of it (or any internal combustion motor for that matter) will raise efficiency and it's power making capability. Think of it as a wind tunnel with muliple out lets. The air will take the path of least resistance just as water will. If you have a path with sharp rough edges you will have turbulance (ever seen a airplane wing with square sharp edges?). Now also as far as the cam goes, this is a sticky area. Longer duration will allow more air in before the valve closes (there's a fine line to this however), as well as more lift which will let it out quicker. Also cams can be much more efficient at certain RPMs as well. This is where you want to let the cam builder know what your plans are.
