There are plenty of things that can cause spark knock on a stock motor. Carbon build-up in the combustion chamber, running too hot, a dirty/faulty MAF sensor, vacuum leak, faulty oxygen sensors, faulty air intake or coolant temp sensor, weak fuel pump, plugged fuel filter, faulty fuel pressure regulator, clogged/dirty injectors, and bad plugs/wires. You've already addressed or plan to address some of these, but you've still got some work to do.
Well, out of all of those issues I've already addressed these:
Carbon build-up in the combustion chamber
- Sea Foamed the top end twice. Also Sea Foamed the oil with my last change.
running too hot
- Flushed the coolant system recently, new 50/50 mix and a 180 degree thermostat. Running temps also verified with XCal2.
a dirty/faulty MAF sensor
- 04 GT MAF installed (technically from 04 F150 w/30k miles), is clean.
- All vacuum lines replaced recently.
faulty air intake or coolant temp sensor
- Sensor input to computer verified to be accurate using XCal2.
plugged fuel filter
- Replaced fuel filter recently.
- Sea Foam run through gas tank twice recently. No lean codes.
and bad plugs/wires.
- Plugs and wires replaced 9,000 miles (10 months) ago. I will pull one off each side and check them to be sure they look good.
That leaves bad fuel pressure regulator, weak fuel pump or bad O2s as the possible problem(s). I've gotten a couple intermittent codes related to O2s in the past year or so...