First off welcome to the forums, good job on selecting either the 8 or 9 personally my favorite body style US wise. I've read the other comments and obviously what you've posted so maybe what I say shall help out.

Check my signature block which is what I make with no issues whatsoever and I live in a high area where vacationers come down a lot. So stop and go traffic isn't TOO bad but it can have it's moments as anywhere else. I have an OG FP green turbo and I'm making good results for only 24lbs that holds all the way to redline and zero knock counts. I've spent a lot in my engine (i.e. kelford 272 cams, ported burschur mani, o2 dump) so you will be spending the same I'm sure to get this gain of power.

I've "heard" people using the stock turbo from the 8's which is the 9.8 and some have the 10.5 turbos. I suggest getting a 9 turbo if you have an 8 and running it off that way if you're trying to save some money. Obviously fuel upgrades, I have the PTE 880s and of course the walbaro 225. I don't personally suggest anything above 1000cc injectors unless you're going to run race gas or e85. Upgrade your FMIC, I have a buschur race core FMIC that does me justice and the aggressive look is there to the T. The stock FMIC can handle 440awhp but it's always best to upgrade the FMIC for better flow, cooling and whatever else. Clutch wise I suggest you replace including your flywheel, I went with Comp Stg 5 and it's pretty good with their Comp flywheel.

Hope this helps some in the questions you've asked minus the tuning since I don't live in your area. But 400-500 hp is achievable and reliable pending on how you drive as mentioned above as it is with any car. FP series turbos are a straight bolt on stock frame set up just have to get the Evo 9 j-pipe if you have an 8 and if you go with a 9 you are squared away regardless when you do the swamp... lemme know if you have any other questions!