I would recomend flashing the stock ecu, but in the past I have used a bazzaz.
their is a plug for the map selector switch. it is a two wire plug with white connector. looks like the one for the two wires for the ignition sensor, but it is not. selector switch is just a simple open and closed switch. the wire on the plug just loops right back into the connector. with it connected it is on one map. with it unpluged or the wire cut it is on map two.
so I had a nitrous map, and a na map. ran the wires from the map selector switch to a relay and tied it in with the nitrous activation so that it switch to map 2 (the nitrous map) when you sprayed the nitrous and only when you sprayed the nitrous.