you can only retard the ignition like a ultiplier, so you'd get shit driveability off boost (think of it like a non-vac advance dizzy and you twist it, you retard the ignition EVERYWHERE)

i'd say megasquirt would run a twinky turbo fine. but if you dont wanna go down the management change route, go for an adon bit of kit like the like the EMS.

i wouldnt personally swap to RS2K ecu, as you'd need to get the whole lot professionally remapped which would be vey pricey, and even after all that it STILL wouldnt be a very good solution.