Misfire Cylinder 4

I recently developed a misfire on cylinder 4 (P0304). I've replaced all plugs and that one coil (Denso for both). Misfire came back so I checked cylinder 4 with a bore scope and it looks like there is coolant in there mixed with the carbon build up and cylinder 2 looks too clean. I've only additionally checked cylinder 1 so far and looks like normal carbon build up. Seems like this is a head gasket issue. Can anyone shed some light? The truck has ~160k miles. Pics of cylinder 4's recently replaced spark plug after driving ~50 miles and bore scope image. Seems to only throw a check engine under a decent amount of throttle and runs fine after clearing the code.