I think the stock components are near the limit with the Edge EZ. Some will say different, but I really think if you choose a TST or an Edge Juice you will have to do some other modifications, and a turbo swap to get the EGT's down low enough so that you can use the box to its full potential. Sure you can use either box with a stock 600, but you will have to watch your gauges like a hawk to avoid an expensive mistake, or if you have a box like the juice with the attitude it will automatically de-fuel to avoid turning your Cummins into a molten mess. But the whole point of a box like that is to be able to USE it, which I really think is impossible with the tiny stock turbo. Personally I don’t want to completely toss my warrantee out the window (although I accept that I am my own warrantee station since I have chosen to use an EZ), or spend that much money, so I went with an EZ, it is a lot of go for not that much $$$
With the EZ I can tow 8,000 pounds up an 8% grade without pushing the EGT’s into the danger zone (above 1350 for me, pre-turbo). On level two, the EGT’s climb a bit high, so I have to watch the gauge, and on level three it really isn’t practical for towing. After some more time has passed and I have some more $$$ in my slush fund I will get the Piers modified turbo, hell for $400. 00 it is a deal.
For about $650 you can put an EZ and an EGT gauge on your pickup. You can tow to your hearts delight in level one, with caution in level 2, and hot rod around in level three. For an additional $400-500 you can add a piers turbo, knock down the EGT’s and tow to your hearts delight on level one or two, and maybe even three. So for a little over a grand you can have a pickup that will tow all day, be reliable, and not be a time bomb.