If your wategate is set to less than 6psi, then yes you can set the MBC to 6 psi. Are you running a direct line from boost source to WG right now? How much boost is that yielding? If its over 6psi, a MBC wont allow you to lower it.
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"So...is there any tread left on the tire..or at this point would it be like throwing a hotdog down a hallway"
-Stewie (Family Guy)