I dont think you are giving us all the information we need. What brand UP do you have on it now?
Did the dealership install the bolt after you pointed it out to them?
I personally would not do anything to your car because as soon as you touch it they are going to say it's your fault and not theirs. You need to get them to take it out on a test drive and get some boost readings. Only thing I would do on your part is reset the ECU by disconnecting the battery and see if that fixes anything.
rollin on 17's now and they're dirty