Yes, but your not going to like it. My sisters car developed a similar sounding noise and I even had it towed to toyota who could not diagnose it. When the engine was pulled (you have to pull it to drop the oilpan) we discovered it was neither piston slap nor wrist pin. Instead, the crankshaft bearing was dissolving itself rather like pencil shavings. A connecting rod bolt had snapped on one side of the crankshaft reducing the bearing to little sheets of metal as it scrapped off with every turn of the engine. I have photos as I believed it to be related to the oil/sludge problem causing poor oil circulation in toyotas.
The engine had to be replaced, we used a japanese import engine, still cursing at the choice-should have scrapped the beast at best.
Source: Gary's Transmissions, Florida