Don't go to the dealer!
The first time I got this code, that is what I did (went to dealer) and they had an engineer come out and after driving my car for 10 miles or so they finally cleared the code. After they cleared it, I immediately went back to install the FRPP tune and the P3015 code never showed up. Keep in mind, the code also would not go away if I put the car back to stock. The dealer at first was saying I needed a new PCM since they couldn't clear the code if you read more in my thread
However, I have since installed this tune several times and each time I do it, I have noticed that this code will show up. You can keep trying to clear the DTC with the procal unit itself and the code will probably just keep coming back immediately.
The solution is this:
The code will not hurt your car so just drive the car around for 10-15 miles varying the rpm's and see if it goes away. If it is like mine and does not, after driving for 10-15 miles, find somewhere to stop the car like in a parking lot while it is running and hook up the procal tuner and go into one of the settings called "profile learning" or something and it says to blip the throttle past 3k rpms and once you do this one or two times, the code should disappear. After it goes away, you can go back and verify the code is gone by checking for DTC's.
I have also called Rey (technical support) at Ford Racing and he said that getting the P3015 code is unique to the 2011 mustangs and that it should go away on it's own after driving the car for a while and that it won't hurt anything. I recommended that Ford Racing update their instructions for the 2011 mustang to compensate for users getting this code and thinking there is something wrong.
Hope that helps, let me know if you have any more questions. Being the guinea pig was not fun for me.
For more technical info and confirmation, call Ford Racing technical support:
Tech Line (800) FORD788