You absolutely must have the turbo manifold, like the ones' found on a 1991-1994 Legacy turbo or the US Spec WRX. There is a great difference between the stock N/A headers and the turbo headers (exhaust manifold). Once you have the manifold in place, you will need to bolt your uppipe onto that. Let me explain one thing about the uppipe to you: for an EJ25, when doing the Legacy style turbo setup, it is recommended that you get a steel spacer to put in between the the bottom of the uppipe and the exhaust manifold. Since you have a 2.2, I am not sure whether or not you need this, as the reason for having it is so the uppipe clears the passenger side heads of the 2.5. I think you will be O.K., but I am not positive. If the uppipe doesn't fit, you will need to have a custom one made or go to a machine shop and have them construct a spacer for you, it recommended you use one at least 20mm thick. I have one on my car and my Legacy turbo uppipe works just fine (no cat!)
Your list seems to be complete, the only things you need are oil feed and return lines, and some coolant line to the turbo. You can get the oil feed and return lines from
www.autocaresubaru.com. I use the banjo-bolt style return line, which requires no tapping of the oil pan, and works just fine (no backed up return line). You may run into some trouble trying to find the right voltage zener diode, so it may just be in your best interest to get the unit from Split Second, it's like $70 (zener's sometimes have trouble in different weather conditions).
What kind of exhaust do you plan on using? What kind of turbo, intercooler? Do you plan on having any sort of timing control so you don't detonate/ping?
One piece of advice I can give is take your time. If you plan on installing the kit yourself, it will take many of trips to the hardware store, and quite a bit of self ingenuity to get it to work right (just figuring little things out, like how to make a brace for the turbo so it doesn't move around).
Oh, one more thing. You might want to get a fuel pump. The WRX units flow plenty of pressure for 5 psi, so just pick one of those up for like $40 in the classifieds on i-club. The US Spec WRX pump will drop right in.
Don't buy a Vortech RRFPR, get a Bell Engineering unit, much better. Mine works O.K., but it is nice to have a unit that responds to each INDIVIDUAL lb. of boost, instead of just 4 psi.
Don't forget all of you gaskets, that is a pain to have to find when your ready to install, so get that out of the way. Oh, and since your going to use the WRX exhaust manifold, you will also need the WRX front sway bar, or else you will have nasty squeeks.
What year is your car, are you sure it is MAP based?
Graham