i asked this question, i found i cant really trust them,they come far and in between,i was recommended one chip used on a modded forester,(and for the life of me i cant remember what it was) but i do remember it was mixed reviews, it connected to a obd2 port, so i dont under stand it all so well...
all i can think of is ask someone with a performance shop that does ecu tunning,maybe they know something...