I have a 2001 F150 with 210,000 miles on a 4.6. I am aware of the spark plug blow out issue and we'll versed in fixing it. I have recently encountered an issue where #8 is melting the boot that goes over the plug and blowing the coil off. It's just the coil that's getting blown off, the plug is still tight in the hole.

 

I don't know how it could blow off the coil unless exhaust is leaking around the plug.

 

... or through it