Agreed. I have stock and apexi together. At bpu an aftermrkt bov is not really needed. Nothing works better at low boost/rpm than stock bov. But at 17 to 19 psi, it's nice to know you have something for insurancesupra400hptt said:Some people use the stock blow of valve at BPU. I don't think there is any hard data out there that absolutely says whether or not the stock BOV is flowing enough when it's working. Common sense tells my the stock BOV was probably designed for the stock boost levels and at 18 psi isn't working as well as an aftermarket. As things go, this can be a pretty cheap mod. I got my Turbo XS for $170. You didn't mention it, but you need some method to increase the boost. Bleeder T's spike bad but cost next to nothing. Manual boost controllers seem to work well and aren't too expensive. Electronic boost controllers work well and can be expensive. You need one of the above before the BOV. I personally like the aftermarket BOV because I can hear it and I know that it's working properly. Couldn't hear the stock BOV on my car although some claim they can.