you can vent into atmosphere if the BOV is before the AFM/MAF, cause the air has been metered after the BOV... if you put the AFM/MAF before the BOV, it has to vent back, after the the AFM/MAF. if you vent into the atmosphere: ie;
AFM/MAF before BOV, when you floor it, the air that just past the AFM/MAF has been metered..the ecu will compensate fuel to match the air that just been metered., but when you shift, the air is vented out into atmosphere, then you get on the gas again and the ecu dont know where the 5lb of air went , so you would bogg because of the air that vented out was metered already and the ecu dont know that.. and it will be rich. i've ran mines: BOV before AFM, vented into the atmosphere for years and no problems. cause the air is metered and when i shift (vents to atmosphere), new air comes in and goes on and on... BOTTOM LINE IS, if you want to vent to atmosphere= BOV before AFM/MAF... and if you want BOV to recirculate= AFM/MAF before BOV