Alright chaps, I'm new to the site but not new to the vr6. Had one about 6 years now I'm a qualified mechanic and got about 16 years experience, currently working for the AA, I noticed you said you changed your Pcv for a catch can, have you blocked the end going into the air intake pipe? If not then I'm more than certain that is why you've got the hunting, it's drawing in air that isn't being monitored by the Maf sensor. And the ecu is trying to constantly try to correct the a/f ratio. Just a thought, hope this helps! Andy.