Well, you got some good clues right there. Definitely something wrong with the operation of injector 5. The wiring, the connector, or maybe the injector itself, seeing as it is only happening when it is hot. Not too optimistic cylinder 3 misfire is fixed but, ha ha. You were poking at your harness with a pin and stuff too, right? And now injector 5 doesn't like it.
Cause you already changed the coil and plug for three already, it is probably the injector giving you grief there, too. The other guy was saying that the wiring for gas injectors causes issues. I don't know about gas injectors in particular, but if it requires fitting new connectors, there is a place for the car to be temperamental for sure. Sounds like a good clue.
I reckon focus on making sure the injectors, the connectors and their immediate wiring are all good.
It is the little things get you. I have had wiring issues myself the last few weeks. I am rebuilding a Trailblazer. Got everything finished, then it had a slight misfire. With no codes. After going through everything, I finally found the spark plug tube seals had the slightest leak and that stuff being blown into them was shorting the spark. Then the airbag, ABS and traction control lights came on. Tech 2 said Rollover Sensor and right front wheel speed sensor. Well, after pulling all the seats and carpet, dash and console out, could I find anything wrong with the Rollover Sensor? No. So I moved onto the wheel speed sensor. Tested that and the connections, swapped right for left, blah blah blah. In the end, I discovered that when I did the engine mounts, I crimped the wire for the sensor behind the mount for the rubber mount that attaches to the chassis. Fixed that, and the airbag light went off with the others...
The majority of pain is self-inflicted.