I get code 78 often. 1995 Chevy 6.5 diesel. Help Please email me.

 

DTC 78 -Turbo Wastegate Solenoid Fault

fairly straight forward-replace the wastegate solenoid(mounted on the drivers side valve cover with the vac lines coming from the vac pump to the turbo waste gate).

sometimes some wd40 in the vac ports will do the trick-most times replacement is needed.
also check the wiring to the solenoid for bad connections or breaks.