The reason they said u need an A/M BOV is because they were to lazy to make a new return pipe for the vented air (when installing an A/M IC it's easier to put on an AM BOV), If u want the A/M BOV on there clean your AFM, AAC valve and every time your about to stop (going about 5KM/H) give it a touch on the accelerator peddle.. i would recommend going back to to standard BOV as you don't really sound like your that confident working on your car.
Before you do a mod research, research, research.... even if your mechanic says you need to do this, this and this to get ...