You're walking down a very well traveled path in the company of people that have been down it many times. The stock I/C is marginal with a base tune. *Any* performance based tunes are going to increase boost which will increase charge temps which will require a larger I/C or the ECU will start to adjust power downward (not sure if it's by reducing boost or timing or both).
It doesn't matter how the tune is loaded, from the AP that is used by practically all of the people on this forum and in North America or by another OBD-II device that is relatively unknown, they all modify the same parameters. RaceChip hasn't found any magic that Cobb or any of the tuners on this forum haven't, they've just packaged and priced it differently. A tune from another tuner *will not* "stack" on a RaceChip installed tune; it will completely wipe it out.
You're new to this platform. The best advice you'll find regarding it is here; nobody has any skin in the game and everything on the market has been vetted. In this case I know that the collective opinion will be that you've gone the wrong way and should return the RaceChip and spend another $100 for the AP's that come up for sale on this forum weekly.
BTW: their aren't any "chips" for the FiST. They all plug into the OBD-II port and modify the code in the ECU. They're called chips because, back in the day, we'd have to replace the ROM (the chip) on the ECU. Call it an OBD-II re-programmer, a chip, a super-duper charger, etc., but they are all the same thing, The devices that devices that modify incoming signal to the ECU to manipulate it aren't "chips" either, and they are a terrible idea for anything other than a stock tune.
In short, get an AP like everyone else.