Only when he clutch is engaged or only when the clutch is out and you are running? Our clutch can be noisy, some worse than others, but with your mileage guessing a throwout bearing. Just a guess though as I have 143,000 on my original clutch and no aberrant noise at all.
Hotchkis Z1 Motorsports JWT Hawk SSR Crawford
ZeeToyz Valentine Sumitomo Royal Purple Zaino
I like my 350 but I love my 300ZX TT more.