Propane will produce the coolest EGT`s But of the boxes I have tried to date, I would have to give the node to the Stealth.
I have had the 90hp Juice, the 140hp+ TST Powermax, the 100hp Predator, the 120hp+ Predator, the 135hp Stealth, and 100hp propane. (NO; Not all at once
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The Predator 100 produced the most heat, then the 90hp Juice, then the TST Powermax and 120hp+ Predator are about the same, then the 135hp Stealth, the coolest without a doubt is the 100hp propane.
Don't forget all the power addons I mentioned can be set to much lower settings, and that will lower EGT`s with the exception of Propane. (the lower you set it the warmer it will get until back to stock temperatures)
The TST Powermax has by far the most power, so much you can not use nearly all of it, The Predator has the most usable toys, The stealth is probably the best of the ones I have used. (only because of the lower temperatures)
The TST Powermax has built in Boost and EGT gauges, and on the fly power/torque switching. By far the easiest to set up and use. So it is my favorite hands down. And once I have the tranny fixed the TST will be back in the thick of things.
I am one of thousands waiting on the release of the new hot Juice with the in cab controler/monitor