I just brought home a 2005 Mustang V6 with the Pony Package. It has some mild mods such as ceramic headers, dual catbacks, CAI, 70mm throttle body and a Diablosport Predator Tuner. I've ran 91 Octane for a bit and it ran good while set to 91 Performance on the chip, however, yesturday I decided to try 87 and set the chip to 87 Performance. It ran fine with a full tank of 87, yet when I switched to the factory 87 Performance tune that came pre-installed on the tuner it totally died, I've tried every other tune including the stock setup yet whenever I go to start it, it revs up instantly to around 2500, goes down to 500 for a bit and then quits. If I work the throttle right I can get short one minuite bursts of normal running above 2000 but then it shuts down. I tried disconnecting the battery for 4 hours and yet it still does this. What should I do?