2002 Ford F-150 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