I would start driving slow, put my flashers on turn my inside lights on if it is dark out and call
the police on my cell.If it is a fake cop the moment he can see your on the cell he will be gone.
As an officer, I would say this is the most sensible course of action. Albeit if it is a thug he may be pissed that you are on your phone and ram you, shoot at you or get information from your plate registration and bother you at a later date.
Calling 911 is a good idea. In bigger cities, however, you may not be directed to the same dispatch center as the UC attempting to pull you over. So driving to a police station is a good idea, or tell the 911 operator that you are going to the nearest Fire Station, or EMT Center, they could probably even guide you to the correct position. I know in Phoenix every call made to 911 from a cell phone is tracked via GPS (if GPS is turned on), and every patrol unit is tracked with GPS they could get a uniformed officer to your location rather quickly. (Note: They -dispatch- do not record every call being made, only those made to 911, dispatch centers, and most gov't lines.)
If it turns out that it is a legitimate officer, be as kind as you possibly can, thank him for his patience, his service, and tell him to be safe. Remind him that he needs to return to his home safely just as you wish to do the same. If he (officer) approaches with an attitude, as hard as it may seem, be polite. Explain to him why you didn't pull over, tell him you respect the law and those that enforce it (even if you don't). Always have a good joke on hand, if you can ease his tension, it will go much smoother for you.
Now, I realize that there are dog bag officer's out there who will attempt to ruffle your feathers, and make things incredibly difficult for you, with these officers it is best to remain calm (you are most likely being recorded) and complain to his supervisor later. Chances are you aren't the first to complain. After awhile Officer Dog Bag will either quit or be fired.
Now, if it is a thug with blue lights, and you do stop...understand that while sitting, you won't get your gun out quick enough to be very defensible and turn the tide. It is better to loose some money and other material items then get injured and have thousands of dollars in medical bills, or worse be killed.
Be smart, be safe, and Stay Off the Wall (or obituary for you Non-LEO's)