Well, that's what you get for not checking with me first.
I suspect you've got a knock (just an uneducated guess) AND bad knock sensor wiring.... some people do mistaken other noises for knock though so take it from the beginning.
First, you need to fix the code 52... you MUST do this first as the extra fuel and pulled timing could be making another, smaller problem sound worse than it is.
Second, you can do this at the start too, check for any loose studs or leaks at the union of head and exhaust manifold; Some people mistaken the sound of an exhaust leak at this location for a knock.
Third, make sure there is spark getting to each cylinder.
Fourth, if you have NO CODES, check the spark timing and mechanical timing. You cannot adjust the timing if you have any diagnostic codes or the engine is cold or idling erratically.
Fifth, with all that checked, check for the offending cylinder. Start the car and have an assistant hold the car at the lowest possible RPM where the noise is still audible. Now pull the plug wires, one at a time, until the sound is gone; the engine will bog, but the sound will be gone. Wear some heavy rubber gloves to avoid getting shocked and don't let the spark jump the gap. If the noise doesn't go away you're most likely looking at a cam related problem.
Sixth, if the sound did go away when pulling one of the plug wires you now know what cylinder to focus on. Check the valves, shims, compression, spark plug and injector. If theses check out, it's time to open the bottom end.