What is the spec stage 2 clutch rated at?
Whether or not you need a turbo elbow is completely dependent on your downpipe/exhaust design. You'll have to check with whoever you are buying that from.
The adjustable FPR isn't necessary, but what it WILL do for you is be able to shift your entire tune richer/leaner (like if your enthalpy ECU comes in too rich and you want to lean it out across the entire RPM range). Definitely something that can be added later though.
Intercoolers aren't really an exact science. You basically want the maximum amount of exposed area (meaning its seeing airflow through it), with the minimum amount of non-exposed area (so as to reduce pressure drop), while also keeping the work-ability of your intercooler piping/bumper, etc. AND you want all that while being as cheap as possible haha. Just be careful when you read "CAN SUPPORT UP TO 600HP!!!", because in most applications, it wont be operating in ideal circumstances (some of it will be covered, etc). Something like this SHOULD work fairly well:
http://cgi.ebay.com/ebaymotors/CXRacing ... ccessories
or you could buy an entire vehicle specific intercooler kit that comes with mounting hardware, piping, directions, etc.