The Daughters OBS was running a little rough off idle the last time she was down. Now she has a miss fire on #4. I did do Seafoam in the Intake and a Lucas Gas Treatment in the Tank the last time she was down. Plugs have been changed to NGK copper core. Going to have the #1 son swap the plug wires side to side and see if the fault follows.
If an injector was leaking the plug would be fouled. I have not seen the plugs, so hard to tell.
Valve Cover gaskets and the Spark plug tube seals were changed about a year ago.
140+ K miles.