Default Boost Activated Powervalve for Blow Thru Carbs

i have done a production run of Billet BAPV's with stainless ball and closed end wound stainless coil spring.. these do not require machining of main bodys to fit ....they are $US58 each and include a 6-32 set screw to block off the PV port feed to main body...with 2 you get a piece of 90 deg bent 10mm AL tube to make a rear PV extension ......10 or more are $40 US each...