Reasons for BLACK THICK SMOKE FROM TURBO in HHP locos

BLACK THICK SMOKE FROM TURBO 
a) CHOCKED AIR FILTER.
b) DEFECTIVE CLUTCH
c) TURBO AIR INLET RUBBER BOOT WORKED OUT AND BLOCKING THE TURBO INLET PASSAGE.
d) DEFECTIVE INJECTOR.
e) IMPROPER ADJUSTMENT OF RACK.
f) MALFUNCTION OF GOVERNOR.
g) SLIPPAGE OF INJECTOR LINKAGE