That is a Custom Pit made in Georgia. Read through the following thread; it starts out like yours (frustrating for a new pit I know) but I think folks with these pits have identified solutions, if memory serves it means increasing the size of the exhaust to get proper low, but yors looks like it might already have a larger exhaust - how big is it?
http://www.bbq-brethren.com/forum/sh...d.php?t=157905
EDIT: Sorry about that, fixed the link to boiler93's thread.