I can't address non-factory modifications, but the hard-starting has a real easy fix. When you replaced the battery, the Engine Computer lost its memory, and it has to relearn "minimum throttle" before it will know when it has to be in control of idle speed. Until that occurs, the idle speed will be too low. You will not get the nice "idle flare-up" to 1500 rpm when you start the engine, it will tend to stall at stop signs, and it may not start unless you hold the accelerator pedal down 1/4".
To meet the conditions that trigger the relearn, drive at highway speed with the engine warmed up, then coast for at least seven seconds without touching the pedals.
If the engine is running better with your new parts, suspect there is something wrong with the original system. It's the fuel and air that makes the power, not the spark. The marketing side of manufacturing is so extremely competitive, if every 5.9L ran better with more power and lower emissions with a different ignition coil, you can be sure they would come with those parts from the factory. Usually it can be done, but not without sacrificing emissions. Then you're getting into custom stuff that few people have training in.
Thursday, January 15th, 2015 AT 4:25 PM