Yes it is turbo charged. How do you chech to see if working proper?Sorry for the delay, glad you found the valve clearance.
From the engine model you gave, that is a turbo charged one? the -T usually means turbo.
I'm wondering if the turbo isn't working properly. If it isn't, it would explain the problems. Less power, black smoke as there isn't enough air getting forced in.
Black smoke means there is heat to get ignition, but not enough air or bad spray pattern causing the fuel to not burn fully.