Megasquirt is a full blown engine management system, for almost any motor out there. Its writtin in high level so it is easily scalable to pretty much..well..anything.
Not just a rom/tuning gui, it is everything. Cool little thing.
Megasquirt II is a add on but packs a punch of new features(fuel and spark control, as well as IAC, awesome fueling) http://www.msefi.com/msinfo/ms2/
Megasquirt
http://www.megasquirt.info/