This started Friday. I drove the car Thursday night and had no problem. there was a big temperature difference from Thursday night to Friday night, much hotter, went from 60 to 85.
I did top the gas off 5-6 gallons at one of my usual gas stations. I'm not getting any knock (cel) that I can tell. I changed the plugs out since they were from last season. Running 12-15psi of boost.
I can't think of what it could be other than either some bad gas or valvetrain noise.