This sound like the girl at the counter the other day with the "clink, clink, whoosh, whoosh, zwing, zwing" sound effects while explaning the problem to the mechanic! P.S. you could see the look of amazement in the mechanics eyes! Anyhow, take a 1/2", 3/8",1/4" extension, the longer the better, place one end on the turbo. It doesent matter where if you can hear the sound in the car you will definaly hear it thrue the ext. place your right or left hand in a cupping fashion over the other end with the open end of your "cup" to your ear. now have someone else in the car randomly excelerate and decelerate the motor if it is the turbo you will hear in thru the extension. Now, if it isnt the turbo you can repeat this process over the entire motor untill you narrow the area of the sound generation. once you narrow it down then start asking the questions needed to trouble shoot your "grinding" sound.. I hope this helps. !!!!!!! do not place the extension on any moving parts!!!!!!