Hi Marshmallow and welcome to the forum

Now where have I seen a car like yours (but in silver!)

Get some pics up when you can

Yes the brakes can definitely be improved upon (see my sig). Just use the search function on here and you'll find quite a few options popping up. It all depends on how much you want to spend.
As for adding the boost guage, It doesn't alter anything within the engine as it is simply a guage and so shouldn't affect your warranty
