it all depends on what your goals are/what the car will be used for/what budget you are working with. for ECU, full standalone will get you limitless posibilities, but its expen$ive for dyno time. Rtek is a good option as a pseudo-stand alone. not as tunable as a standalone but at half the price, with bolt in installation, and the stock map still present, it makes an attractive option. I think I read somewhere that the power possibilities are anywhere between 300-375 depending on supporting mods.
Injectors are all about power goals as well, not much to talk about here, just make sure you have the *actual flow for your use. sometimes the advertised flow rates aren't actual flow rates. Be careful.
as far as turbos, hmmmm what is affordable? no matter what aftermarket turbo you chose, you are looking at a new manifold to match as well as custom downpipe, even external wastegate depending on the turbo. another option is a hybrid such as found on
www.bnrturbos.com. once again install is bolt in and power is in the 300-400 range depending on stage. with the hybrid there is no cusom DP, no new manifold, so it is more cost effective and way easier to install.
one question... why the S4 parts on the S5 keg?