This is going to sound really dumb. But has anyone checked the header gaskets? A small exhaust leak has the exact same noise as a bad valve tick. And goes away under certain pressures if its on something like a gasket. Somebody grab a sniffer and check this out. Because on my car you can hear it below the engine more than above. And the way these cams sit on top of the head. The noise would always be there. At idle and load. You would be able to hear it at the top end. But if its louder in the wheel well. I would look at the headers.