Gremlins

I'm using an AutoTap Enhanced Scanner. DTC is set indicating misfire [Lean ?] on cyl #4. Routine maintenace was to install new plugs and wires. More recently swapped out injector #4. Car ran fine for a few days, but first trip at 25 mile distance caused problem to return.

Pulling hair out. Seems isolated to that cyl, but prob does not manifest itself except for a longer than normal [for me] drive. NO other dtc. Fuel Press etc is normal.

Once problem shows up, it doesn't want to resolve itsef, except once when letting it sit for 4 days caused a spontaneous resolution. Why???

Could I have some sort of PCM problem that reflashing the prom could fix. Definitely stumped on this one. All suggestions appreciated.

What year and engine do you have?

Do air induction system cleanup! The best solution to such problems