So looking here
https://lmr.com/products/79-93-fox-body-mustang-spark-plug-gap-specs

It shows that the correct gap for my car (completely stock) is .054

So that's what I set the gap to... BUT... then I realized the plug I was using is NOT the "ASF-42" since you pretty much can't find that plug anymore.

The one I installed was "ASF-42CA."

So I'm wondering if the gap is too large on the plug since it's not the same plug?

Or is .054 correct?

Car seems to be running correctly...

Correct Gap For 1991 Mustang GT With Motorcraft Plugs