I do agree with TnP that the turbo has a cooling effect on a diesel that it doesn't on a gas engine. Because the diesel doesn't require a precise mixture ratio to run properly, increasing boost without increasing the amount of fuel will lower EGT's, but higher boost without adding fuel doesn't increase power and increasing the amount of fuel beyond the engine's capacity to supply the air to burn it will just result in black smoke, whether the engine is diesel or gas.
Fuel injection has been standard on gas engines for so long that most people either haven't seen or forgotten the sight of black smoke coming from gas engines with badly adjusted carburettors or malfunctioning float valves.
