The 3sgte power primer that is still floating around the internet is a bit outdated to be sure. Umm to give you a rundown of things you could do that will net you sub 400bhp...To include some obvious ones...
Water/meth injection kits = there are a good deal of kits floating on the net these days that are all worth your pretty penny.
NASIOC.com has an entire forum dedicated to these kits and instead of repeating from there ill just post a link to that forum.
http://forums.nasioc.com/forums/forumdisplay.php?f=145
Chargecooler/Intercooler = Some people will say get rid of the chargecooler (failbox) and opt out for a front mount intercooler.No need to exaggerate on that becuase the net is full of info about front mounts. But in the regards to getting the most out of your chargecooler for sub 400bhp, i would suggest:
-Running your current pump full time
-Replacing current pump with a newer better version
-upgrading your heat exchanger for a larger capacity one
-Getting larger chargecooler either through a third party or making your own
-lagging chargecooler with heat wrap to prevent heat soak
Boost controller = There are two main types. Manual or electronic. Manual gives you the ease of simply installation and stupid cheap for what you are getting. Electronic esp the higher end types, gives alot more precision and other bells/whistles (such as display of boost pressure/other parameters, tuning based off of RPM etc.) but comes with a higher price. (personally i choose the electronic all the time).
Downpipe/3-5in exhaust = Alright while some people will say that you can get away with a 2.75inch exhaust and will pull out all types of maths to prove it, a 3in exhaust will be necessary for sub 300-400bhp. Same for the downpipe. I belive there are 2-3 companies that still make downpips for the 205/3rd gen 3sgte specifically but im sure there are others. Also i will try to dig up an old link to a HUGE discussion on the advatages or trade offs with an increasingly larger exhaust when leaving the turbo.
Well imma stop with this as im still hungover from last night but some quick points to consider..
ECU Tuning vs the cheap DIY methods
Turbo Upgrade time!
Later today ill post up a huge post full of links to things where you can buy or learn more about the stuff above. I mean btwn all the forums that mess with the 3s engine there is alot of info and tons more that i didnt even mention. Also im sure the other members here will post up some useful info as well!