There was awhile where I was in the 160-170 range as I learned how the kettle reacted to vent manipulation. Also had temps in the 260 area for 5-10 min at a time as I got control. I usually am grilling on high heat so vents are wide open.
Well, I have to say that your cook has me completely mystified. Long story short, it shouldn't be possible. There's a piece missing somewhere.