I can give you a run down of what to expect if your considering going towards the RBC + Injen CAI Combo.

As far as problems your gonna experience with a simple bolt on installation is idle issues, not too severe just a bit of getting used to and the CEL problem. both problems are likely to be fixed by port matching the RBC and ECU tuning. The sound is great - http://www.youtube.com/watch?v=_OY1pQD4nFg

IMO from my setup, the gain in top end isnt worth the loss in the bottom end, it defeats the purpose installing an upgraded item. If your gonna go down this route then be prepared to spend extra on making things work out positively for you. My first stock dyno result was Max 91.0 KW, below is the results of after installing the RBC and CAI. Stock indicated by the Red Line and modded indicated by the Blue line



Good luck, hope that helped.