in the bit that has your user name and amount of posts etc it says that you have a R34 N/A but you are saying you have a R33 N/A.....which one is it????
My first (well second really) question to you is : what are you wanting to achieve with your car?
Why do you want a Blitz ECU? Why not go with a GReddy Emanage, or even a Apexi Power FC???
Generally speaking, if you want bigger cams, its always a good idea to get head work done aswell so you get the most out of having the bigger cams, then you may have to consider about upgrading your fuel injectors too.
You shouldnt have to worry too much about getting an overly stupid sized bigger throttle body, i would recommend talking to your tuner and seeing what they recommend.
In regards with the intake setup, generally you can just get a pod filter, and have a cold air intake set up to go to the pod.
Also you will find that you will not be able to use RB20 cams in a RB25 engine.