If your asking these questions...you shouldn't be modding these kind of cars...sorry to be blunt. There is LOTS of information out there you could be reading and learning about the very things your asking...instead of saying...is this good...or that...or can I do this...or that.
You NEED a tune with a cam if your going to beat on it. IMO, you NEED headers...let it breathe. You don't need bigger injectors but if you plan on running a sub 3.1" pulley...get them now. Then you'll need another tune for the new fuel map required with the new injectors. You can run higher ratio rockers on a smaller cam like the VS...but when you get into bigger stuff like the S1X or XP...just get the stock sized ones...Rollers if you want to. For the install kit...buy the cam kit from ZZP. Done.
