CT, It's funny to hear your story and then you hear about others who can't get theirs to reach high temps. Go Figure!Were you using a different brand of lump than usual? Some brands burn hotter than others. Did you dump in any of the charcoal dust that settles in the bag? This might cause a temporary spike in temp, I know it increases the likelihood of flashback.With you having the vents closed down like that, I don't see how it could get up to 650 the way it did.