You didn't say 'cap and rotor'- mine had no tip left on the rotor at all when I finally looked at it. That helped a lot. Motorcraft parts, here-
a lot of the others are truly poo.

And seconded on the MAF sensor- mine had a regular misfire that eventually turned out to be the MAF. Again,
aftermarket sensors don't work- but a couple of junkyard ones both did, so now I carry a spare.

I too very much like the big six- lots of torque, and it sounds right!

t

 

OP has a '91. No MAF sensor until '96 for the 300.