I've been chasing a squealing noise when on hard boost and after initially changing the alternator belt as it was just like that noise but no joy. Checked the tensioner, cleaned the alternator and pulley wheels but the car was boosting well and pulled hard but still the noise.
After chasing this seriously for a couple of months as I thought it was getting worse I spent some time on the forums and came across a couple of articles about squealing Golfs and loose exhaust manifold bolts. So this morning I spent a couple of hours checking them and the top right two and bottom right hand were so loose I could twiddle them by hand. I used my 12mm deep socket 3/4 inch socket to tighten these up and a 12mm spanner for additional leverage to ensure they were nice and snug. Unsure how tight to go as I don't want to snap the stud but I think I may need to replace these nuts with new copper plated ones as someone has replaced the manifold and turbo at some point. Will look up the proper torque specs and redo when it's not raining.
I also took the time to remove my plugs, clean and regap to .8mm before refitting and torquing up to 29nm.
