i think that no matter what BOV you use its going to act the smae way because of the MAF. i had the TXS type h RFL and all i ever did was backfire, stall and shoot puffs of black smoke. i adjusted that things so many times it was hardly worth the effort. i am pretty sure that until there is some sort of engine management that comes out for the STi that will take into account an atmo BOV these problems will be persistant. i put the stock one back on and have had no probs since.