Like many others, I hear a ticking sound also but when I lift the hood and put my head down a bit, it seems to be coming from the front (cooling fan area). Not the valve covers or either side of the engine.

Build date: 6-03

 

if it's low pitched and only heard at idle it's normal,

 

There has been a issue discussed regarding a pulley update on some 4runners but I think your production date is well past it but it was creating a noise in the front of the engine. If it is the typical valve noise, is wil be louder inside the drivers side wheel well (the thin exhaust manifolds increase the sound).