Wife's 91 with 47K miles on it.
Been driving years with a slight misfire.
Got progressively worse over the last few months.
Owned it since 2002 and never had the plugs out.
***Odd discovery*** (4)
FR2LS left side (4)
FR3LS right side
Replaced with AC Delco 41-602.
Huge difference and runs smooooooth now.