from what i have found , the cam phasers in the early build engins have 3 hollow pegs that collaps and allow the phaser to move arond to much causing the rattling noise.the other issue i find is low oil pressure.if you check with a mechanical gause hot versis cold you base pressure falls off to around 10 psi,the cylinder heads get only half of the oil pressure.when you get a code for bank 1 and 2 over/under retarded then you will likly have to cheat and shim the oil pressure releif valve and run a thicker weight oil if the phasers have been replaced.usually the low oil pressure is because the cam journals in the head are worn and dumping oil pressure.