What exactley does it mean to "stack" power modules on diesels?

Using a box such as the edge with a software tune loaded up from a programmer such as a bully dog power pup or a predator. Trying to get more power out of both combine over the hp either can provide on its own......does this help?

So the Edge goes under the hood...and then you would hook something else up to the OBDII port(superchips or something like it) as well? or would they both be under the hood?

Edge stays plugged in, control unit in cab. It does not reprogram the ECM, it modifies the message the ECM sends on to the components (injectors, etc...). Predator plugs in to ECM, reprograms it, then unplug it while driving, until the next reprogram.

What D.Maximus said.:D

The way I understand it is you have one type of box, programmer...etc that modifies fuel pressure and/or turbo boost, and the other type changes the injection pulse (advancing it and lengthening it). Anyone want to expand on this or correct me if I am wrong?

Alright...I get it now...can you also have an under the hood module plugged in and one that plugs in inside the cab?

I guess so, not really sure though. I think it just depends on the combo of products. I have the duramaximizer that has a connector plugged in under the hood (can't remember what connector, but it was a PITA to get to!) and the little control box is tucked up under the dash. then I have the edge plugged into the main connectors.

With all of the threads you read on here most people will say that you only gain small HP numbers when stacking....But still worth a few extra ponies in my book..