Max A/C kills engine

If you are using the OE box and controls. You might have a vac leak with the hose circuits that operate the Max AC selection. Either at the control box or the actuator.. Might be a bad actuator at the blend door. Have you tried idling the car higher and tried Max AC? Does the blend door on the right side of the box move up to close off the outside air? If not, remove the vac hose from it and cap it. Try again, does car die? if so issue is further up, bad hose or control box.