cylinder 5 missfire low compression
Rings or Valves with valves more likely. Have a wet and dry compression test done. If the wet compression is a lot higher, it is the rings.
So I looked up the specs . . .
For the 4.2 liter straight 6, which I assume you have, it’s 215psi.
Just how low is the compression?
Without even being there, my gut feeling is valve train
I also suggest a cylinder leakdown test. I suspect you’ll have quite significant leakage, and it’ll be from the intake valves.