i'm going to have to agree that you should slow down
As much as I hate both cops and speed limits, it is so far from wise to take a car that you have owned for one day and take it to 120mph. I'm not going to take some kind of moral highground saying that you are going to kill someone else, cause chances of that are quite small, and I know that if something like that did happen you would be dead anyway, which you certainly don't want. I don't know what other kinds of cars you have driven, but these cars behave very differently from mustangs, camaros, bmw's, hondas, or whatever else you have likely driven. I'm not knocking your driving skills or anything, and I don't know where you hit 120 or under what circumstances, but at least get used to the car before you go pushing it to speeds like that. I myself have hit speeds in excess of 140, so I am not saying that driving at high speeds is reckless regardless of conditions and circumstances, but not in cars that you don't know inside and out, and certainly not in cars that are having mechanical problems to begin with. Once you get your car running right, and you have experimented with it in empty parking lots and you know the abilities and limitations of your car, trust your own confidence in how fast you want to drive, not speed limits. But don't assume this car behaves the same as your last car, cause that will get you into an accident.