Read my Plugs

You want a power valve rated about 2" lower than what you have at idle in gear. If your primary jetting is on, your idle screws should trim out between 2 and 4 turns give or take a little. You may also be exposing your transfer slot trying to idle with that cam. You can either adjust the secondary stop screw to get a little more air so you can back off the idle stop screw or drill small bypass holes in your primary throttle plates. If you have the idle screws at 1/2 turn or less it is likely the transfer slots are exposed or you have a leaking power valve.