If it's the 4-speed ShiftTronic SportShift whatever, don't use the shifter. Keep it in D3 and weeeee.

Anyways, to your question, I'd personally go with a nitrous sytem that's regulated and pressurized based on current conditions. ZEX makes a kit for around 5 bills that'll do it, and I believe NOS (Holley) does as well. nX claims they do it, too, but i've heard a couple of LOCAL unsuccess stories using nX, one resulting in a D17 giving out, and one resulting in a Teg that had nitrous activated at like 30MPH on a busy road.