Secondary Air Injection Crossover

I have to admit, this question seemed simple at first but then the answer seemed to evade me once I started looking.

I have a parts list which shows an exhaust manifold plug by the ford parts number (but no description):

Ford D9ZZ-9G458-A

If that is the case, Google says it is:

M18 x 1.5

But, I remember years ago plugging these on other Ford vehicles with a spark plug (believe it or not). If that memory holds true it is likely:

M14 x 1.25

I'm 99% confident one of those two answers is the thread and pitch size you are looking for. :unsure:

You should be able to source the plug(s) at Fastenal or