So my car has this tapping noise most of the time, sometimes loud enough to set off the knock sensor. Been fighting it forever. It comes and goes, and the filter is clean when we cut it. All of a sudden yesterday, the damn thing stops doing it. I put in my new injectors, fired it up, and drove around. It did it a little at first, as usual, but it just smoothed out, and was quiet. WTF!? Thought it was a bad lifter, but don't know. Its colder now, so my oil pressure is up 5-8 lbs, but thats never helped in the past. Tried heavier oil, too. Ideas?