Stacking...

Lots of guys were "stacking" early on in the DMax performance attempts, but I never thought it was a good idea. Basically, most of the boxes will "lie" to the stock ECM to persuade it to do what they want such as lengthen the pluse width and timing, they also take information coming from the box and modify that on the way to the various controlled systems. When you stack, you have multiple boxes in-line with each other, lying to each other, and modifying the modified settings. Understandably some boxes "stacked" better, and some settings on the boxes worked "better" combined than others. It was really a sort of "black magic".

While this was necessary early on to eke out the last bit of power, it was understandably plagued with drivability problems including stalls, stumbles, "bursting", and such like, though it didn't seem to do any permanent damage to anything other than the trans which was lacking in upgrades at the time. Still, it always worried me since stacking could easily take things WAY outside acceptable limits and do some real damage. At least that was what I thought, even though I don't recall any major failures. <shrug>

But now, it's no longer popular due to the availability of HUGE power boxes. You can now get a single VA box for the DMax that will reliably produce in excess of 500 rwhp and very few drivability issues (trade-offs really, not the stuff that came from "stacking"). And Edge as well as other competitors are not far behind. Basically there are not integrated solutions (single boxes) that provide the power benefits without the drivability and potential damage of the "stacks" while also avoiding the cost of multiple boxes and experimentation to find combinations that worked.