I called and spoke to some people about it. The way I understand is that Cat designed the engine to have plenty of spare boost. It compensates for altitude by adding more boost. At sea level, it is using very little to maintain 177 hp. At 10,000ft, it is using quite a bit, but not all.
Both the EZ Jacker and TD/Speedwerx reflash do the same thing, but in a different way. Both increase the boost to maintain a hp. Problem is, the turbo is not that big and eventually you will run out of turbo no matter whether you have the EZ Jacker or Reflash, so there is a limit to how much hp can be gained from either without a bigger turbo. Most I have read about or talked too say 220-240 is about all you are going to get out of the stock turbo and you may have to run some race gas to get it so you do not have detonation. A meth kit and race gas may get you a little more.
The EZ Jacker and Hi Jacker basically intercepts the signals from the ECU and modifies them. The ECU plugs into the EZ/Hi jacker and then the EZ/Hi Jacker takes the stock signal and modifies it. Only difference between the Ez Jacker and Hi jacker is the Hi Jacker has adjustable power setting and tuning capability. The Ez Jacker is simply plug and play.
The ECU Reflash modifies the stock settings in the ECU so the signals coming out of the ECU are already modified. The ECU reflashes have different settings so you can adjust power. The Hi Jacker does too. EZ jacker does not.
I decided to go with the EZ jacker for simplicity. One hp setting so I don't have to adjust clutch wieghts and settings for increases and decreases in power. I also wanted to be able to put it back to stock if I needed to.
Most systems require an aftermarket can to get the most out of them. Still, for the money, it seems to be about the most cost effective way to pick up 30-40 hp I have ever seen in a sled. You do have to take your ECU, remove it and send it to a TD dealer or Speedwerx for the reflash. You can also buy one already done off the shelf and send your back in for credit. The Jackers, you simply buy and install. Takes about 30-45 min.
Well, that is the jist of it as I understand it. I am sure some others have a better understanding, but that seems to be pretty much it. Good luck on whatever you decide on.