1. Don't just up boost, there are better ways of doing things. Get a proper tune to match the boost.
2. Get the 3 gauge center pod, much nicer. Boost, oil temp, oil pressure would be my choices. (get a sandwich plate for mounting the sensors for the oil temp/press)
3. Don't bother unless you get a custom tune for your car. Verso from ASG would be the best value for money. Otherwise ECUTek Stage 3. Alternatively standalone
ECU if you are using RMS (as they don't offer the retunes of stock
ecu).
4. Turbo does not equal bigger boost. Best bang for buck combo is STi TMIC + VF34.
5. Waste of money unless you want more intake noises.