It was as piggymac said in his post. Followed his advice and managed to get the EGR pipe off and found that the lower flange was warped and it was visibly evident that exhaust fumes were letting by. Getting the bottom bolt of the lower flange off was quite difficult as there isn't much room to work in, only able to get the tips of 2 fingers to reach the bolt. After rubbing the flange down with lubricated emery cloth I managed to get it flat. I made sure there was liquid gasket on the surfaces and after a lot of swearing and cursing I managed to get it all back together again and to my great relief, on the test drive, the squealing had gone. Whoooppeeee!!! I would suggest that if anyone has an intermittent squealing sound, before spending megabucks on belt tensioners, alternators or pulleys, take an hour or so to strip down the aluminium EGR pipe, it may save you a lot of money