low rpm pinging

I have a 2005 mustang gt. my car had lifter noise that quite a few early 05's had. It was repaired at a ford dealership, but since  then I get a pinging sound at around 3000 rpm at part throttle. Ford says everything is within specs and it is normal to hear this. I have a jlt cai, bbk pulleys, x-pipe and magnaflow mufflers. I have even had the car dynoed and found it was running lean and was enrichend 8%. It ran better after that but still had the pinging. I even brought down the timing 2% and it didnt make a difference. I always run 91 octane! And also at wot throttle after 3200 rpm's it is just fine. with all the mods it made 269 to the wheels. Please give me some ideas because nobody seems to have any answers. Thanks!