Mr Morlock wrote:manga might comment. Since the the deflection can be checked from the top that should readily indicate if it is overtightened and that is easy to access. I guess if its like a violin string it would not be a good thing. The other things already replaced seem almost certainly point toward the belt being the cause of the noise.
That's true. In fact he can check it without ever going anywhere near that mechanic again, providing it doesn't need further adjustment.
Just reading back through the thread I realise there's also a worrying mention in the first post about looseness in the crank pulley after the belt change. Apart from the likelihood that this causes belt vibration, and hence belt whine, it is the single most common cause of failure of these engines. The loose pulley must be sorted.
This means that so far this routine job has resulted in a loose crank pulley, an indeterminate whining noise at the front, a damaged cam cover gasket and at least 2 repeat visits. When jobs go bad like this you get stuck with that nasty choice about whether you take work back to the same mechanic for rectification and risk further damage or do you just cut your losses and go to someone more competent.