The issue with the C3. 2 box is that duration without a timing advance results in a net retardation of timing. Here's how it was explained to me (I'm not a combustion expert but i try to listen carefully

).
As RPM increases, you have a vanishing time window of opportunity to squirt fuel into the cylinder and take full advantage of the power stroke. As the piston decends from TDC, cylinder pressure decreases. If a portion of the burn occurs after TDC the resultant expansion of gasses occurs at a lower cylinder pressure and is less efficient at transmitting power to the crank. severely retarted timing (like 100 HP with duration only) probably results in more unburned fuel.
So the VA box gives the fuel, but the retarded timing results in high EGTs. yes you can always add air, and I have no doubts that the VA box can be tamed with a big enough huffer. My point is that it runs hotter than any other box out there and probably hurts fuel economy depending on how you drive (when I was testing it, I got no decrease or increase).
now then, there is still a very attractive option of stacking the VA duration box with a simple pressure box such as the EZ, Quadzilla, Bullydog. These pressure boxes, especially on their mid-range settings, are weak in the low end, but come on strong at the high end. ergo, just the opposite of the VA C3. 2.
so the stack provides these advantages:
1. you get better low end than with just a 50HP pressure box
2. you get better high end and better EGTs than just a duration box
3. you can still get around 100 HP (est. ) without raising rail pressure beyond about 24,000 (a pressure box on 50 HP)
4. This isn't important to all, but such a stack will feel stock at low throttle levels -- you don't even know the boxes are on until you get on it. I found the Quadzilla + VA combo to be very nice in that regard.
Alas, however, the stack still runs hotter than pure pressure at 100HP. But for those who are nervous about 100HP via pressure (rail pressure) this is a good approach. 100 HP via pressure requries more huffer anyway...