I think you hit it on the bead when you said you should've gotten a manual
Seriously though, all the piggybacks feed the PCM simulated load values so that it thinks it's stock and the more power it makes the harsher the shifts will be. The Vishnu flash may help with this so you may want to talk to shiv about it. Then again if you're through the hassle of pulling out and shipping your DME just to get a flash you're probably better off going the Cobb route.