Could the pop-whiz noise that Nicks car made possibly be a turbo waste gate dumping? That’s what I thought of when he said he hears other cars make that noise. I’ve heard that kind of noise while biking.
I’ll second that. We work on a BUNCH of those cars. The 1.8 turbo models make a sound just like he’s describing, which is normal, and caused by the turbo system.
Yes, it sounds to me like he’s hearing the by-pass valve evacuate the pressurized charge.
If Nick has heard this sound from other cars, as he said, then it almost has to be the turbo. I can’t imagine any problem causing such a bizarre sound on multiple cars.