If you are going to fire it up, fire it up and let it scream, yes it will be loud but if the motor has already been broken in, what is thier to listen for? Screw the neighbors, that's like someone else controlling your behavior other than your mom, dad, or wife (or boyfriend HEEE!). You won't burn a valve with open headers. Any cop will cut you slack if you are in the process of making your car law compliant. Otherwise, that cop will look like an azz in front of the judge explaining why you were given ticket for loud exhaust while on your way to the muffler shop to get it fixed. And credibility is everything to a cop. I just wouldn't be out for cruises in the current condition of your car. As mentioned, Cherry Bomb header mufflers still sell for about 18 smackers apiece. Lastly, if you are pulled over for loud exhaust, and they try to ding you for no windshield, you can say you were going to fix the exhaust first, as it it the most annoyance (in some peoples eyes) so you can take it to the windshield shop to get that fixed. A restoration in progress, if you will. It is just creative story telling, very simple.