I could write a book on this one.....
I'll try and keep it simple
Each box has a dwell to recharge the coil
The windings or resistance of the coil will determine how fast it can recover and how much voltage it'll shoot at the plug
The stock box and coil are what we call a Low Band ignition system, designed to run from crank to about 45-4800 RPM after that they will drop off and the output to the plug will fall to below 16KV which is what we consider failure. As it starts to approach it's max operating speed it will also start dropping some cylinders and retarding the timing.
The Orange box is notorious for retarding the timing, from about 5200-5800 it's going to pull out probably 8* of timing, we just throw that stuff away.
Standard Motor Products used to make the best General Purpose ECU their LX101 and it would work with about any coil to the max of the coils ability anyhow up to about 5800. Unfortunatly they bought Echlin last year and discontinued the SMP LX101 and opted to make only one ECU and because the Echlin unit was so much ccheaper to build they went that route instead of maintaining the quality that SMP has been known for for 100 years.
The Chome box is faily decent when teamed up with the correct coil like our FBO Dual Pattern Coil
Here's some test results that we conducted, the rpm is where the system either started dropping cylinders, KV dropped to below 16 or the timing fell back over 2*:
FBO Box #A688...FBO Coil #G642...8800 RPM
Chrome Mopar...FBO Coil #G642...8800
FBO Box #A688...MSD Blaster 2....5300
Chrome Mopar...MSD Blaster 2....5300
FBO Box #A688...Mallory 29216...4500
Chrome Mopar...Mallory 29216....4500
FBO Box #A688...Crane 730-0020...3800
Chrome Mopar...Crane 730-0020...3800
FBO Box #A688...OEM Coil.......4500
FBO Box #A688...Accell 8140....5500
FBO Box #A688...Accell 140001...5500
Mancini Brand...Accell 140001...3500
Orange Box....Accell 140001....4200
Orange Box....MSD Blaster 2....4400
Orange Box....Mallory 29216....3800
Orange Box....FBO Coil #G642...5400
You can see here that the coil is critical to the overall performance and when the correct coil and ECU are matched up the result is a perfect system.
We worked for 2 1/2 years on our box and coil combination to make it work right, since Standard dumped the LX101 the demand for our ECU's has been brisk to say the least.
Go to our tech section and read the articles on ignition and tuning, I'll think you'll find all you questions answered there:http://www.4secondsflat.com/Technical_Information_for_Ignition_and_Carburetion.html