from the research ive done...injectors..fuel rails are not needed since the stock ones can handle more than enough...also i do agree i should do my cams first before my manifold.
Good man, right on with all that.
Installing some high compression pistons is a good idea if you want to install some big cams. If you don't want to do pistons, stick with a smaller cam upgrade like OEM ITR or CTR cams, Skunk2 Stage 1's. Something mild like those will minimize cylinder pressure losses. To regain some lost cylinder pressure you can install a thinner headgasket like a Spoon or Mugen gasket, that'll gain you back a couple tenths of a point of compression ratio. When upgrading cams, you should also upgrade the valvesprings. OEM Type R springs will work great with OEM R cams. Getting aftermarket valves or retainers won't be necessary.
We can't say exactly what to do with your ECU till we know what year you GSR is.
If you want to do your IM install right the first time you should also buy a TB for it, and make sure it's portmatched to the IM.
Keep in mind the Hondata IM gasket too, good cheap mod that is a no-brainer to do while you are swapping out the IM. Don't forget about it.