I think after reviewing the advice that members have given me on this forum the most likely cause of the limp mode on my 05 STS 3.0 Di is overboosting. I have not yet fitted a Boost guage or EGT guage, but will down the track. Having read the recent issue of 4WD action it states if it happens occasioinaly its ok, if it happens regularly get it checked by a professional. It happens on mine everytime i accelerate over 80kph up hill, my question is what problems could this have caused internally so far? Having only done 2000kms since i bought it, what if the problem has been there for the last 108,000? If i fix it now and it stops great. But what damage could have already been caused and what can i do to make sure i'm not just throwing a band aid on the problem? I'm happy to take it to a pro, if i can find one in Adelaide!