If you are going to do 10 psi, you should get bigger fuel injectors. If you do around 6 to 7, you don't really need them. I only ran 7 psi on my Civic with a GReddy kit and I did not need different injectors.
As for hp out of the GReddy kit on the DOHC ZC, I really don't know how much it will produce. I am also looking for other turbo kits that will fit the ZC, but I have been unsuccesful. I know you can just aquire parts here and their to make a turbo kit, but I feel better buying everything at once, that is why I am getting the GReddy kit.
You should always use an intercooler when using an aftermarket turbo. It is just the safe thing to do. I used the GReddy intercooler on my Civic, but I am not sure the exact numbers on hp gains. That intercooler kit will run about $800 and is definatley worth getting. But their is definatley noticable gains.
Increasing the boost will always damage, or push the engine to the limits if it is not built for it. I would only do it at the track.
