The most important part here is installing the stronger exhaust valve springs. When you close the butterfly valve, the drive pressure will open the other exhaust valves.
As long as you shut the exhaust brake, one should work just as good as the other. I did the 4" pac-brake with air because I already had on board air from a remote mount 12 volt compressor. I simply installed a little air switch on my shifter (removed from an old Kenworth heater control) and eliminated all the electronics.
I have to turn the air compressor off if my dad drives the truck. He can't half hear and has big 'ol ham hocks for hands so he will accidentally hit the air switch under a load. Not good. lol
When installed correctly, they are a wonderful addition.
We are currently working with Wayne on the "Thunderbrake" to try to get this thing of theirs to market. Then, people will really hate the old 12 valve.