 The 5.4 Triton V-8 and the V-10 are blowing out spark plugs thru out the USA.  If you google this problem you will find out there are only 3 threads for the spark plug to grip to and the heads are aluminum.  Sorry no fix as a heli-coil is made of steel and it heats up ar a different temperature than aluminum, then the heli-coil also blows out.  This happens on Ford super duty trucks from 1999 thru 2005,  Be careful not to purchase this poorly engineered garbage.  Dont believe me?  Google it! ~!!