2002 Ford F150 coil holddown bolt

i changed the plugs and the boots in my 5.4lt and i had 1 coil pack retainer bolt that will not come out , the nut sert is spinning i tried to clamp vise grips on the plastic surrounding the nutsert which is part of the intake but i cannot hold it i guess the bolt has seized up in the nutsert. i thought about cutting the head off then try to remove the bolt and nutsert from it's plastic then install a nut and new bolt but i dont want to break the intake manifold,the coil pack has to have downward pressure just to hold it in place have you any advice it will be greatly appreciated