Not an expert on the 2KD-FTV engine, but having become somewhat of a "purist" over the years with experience of lots of desi jugars, I would not recommend playing around with this engine unless you have very deep pockets and some very techy speed shop friends.
Theoretically, larger intake and exhaust would increase engine power. A larger turbo would increase speed and there are probably other parts like a programmable chip which can be used to fine tune the engine for performance.
However unless you are able to find some very relevant parts / information on the net I would say that don't play around with how Toyota have set things up. Local mechanics do not understand the D4D engines well and there are some issues with compatability with local diesel so be very careful not to mess things up in the long run.
I do believe that the 2KD is a modification friendly engine and there are probably lots of parts that you can import, use google and do your research if you are serious.