Joining the test-mode connectors (same ones used to reflash) will drop IAM to zero, but I don't know if it will affect which ignition and fueling tables are used.
Try logging the "map switch ratio" parameter and toggling the connectors. If it moves between 1 and 0 then you're onto something. The catch is that in most ROMs the ratio also changes when driving ("cruise" vs "non-cruise"). The tables that govern the aren't included in the open-source ROM definitions but that could probably be addressed if there's interest.