I have often heard how the stock exhaust on the turbo lacks a note. Well, on my turbo, it usually is fairly quiet. Except, if I give it a bit of welly at 1800-2000rpm, especially in 2nd or 3rd, there is a fairly loud note (almost sounds a bit like a fart at times coming from the front of the car), that is there as the revs pick upto about 2500 (by which point the turbo is fully spooled), and then disappears (or gets quieter) again. Is this normal?
Also, on the turbine side of the turbo, there is a grey cable running from it. Is this some kind of sensor detecting exhaust pressure?