Are you lighting the coals inside the UDS or adding lit coals from a chiminey, etc to the firebasket? Starting the fire in the UDS can let it get much too large and take ages to cool back down to proper temps. If you have two intakes closed off and one with a valve, does that valve change temps as you adjust it? If you add lit coals, 6-8, to the firebox and have two intakes closed and the valve open you should be able to begin closing the valve aas the temp goes up to get it to a nice 25-250 without a problem. Keep the Exhaust full open What happens with the 2 intakes closed and the valve closed? You need to find where the air is getting in and feeding the firebox to get the temp that high. Lid/stack leaks likely would not do it.
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