My buddy chino did the same thing, but I don't think it was due to the SAFC2, just one piston melted, others were fine.
Same thing, long highway pull @ 18psi with FCD and SAFC2.   Wideband said it was fine tho, and no detonation.  He's been running that setup for over a year.  
Either it was electrical (injector harness wire) or the injector failed.  It was the #5 piston if im not mistaken