Here is something to read, I found this, hope it might be some help to who all reads it.
BBQ Tuning Plates
How to adjust BBQ tuning plates the first mistake most people make is adjusting the plate before the BBQ Pit has come up to full temp.
Allow the BBQ Pit two hours to heat up. Just because you see the temp gauges shows 250 degrees or so does not mean that the pit is actually heated up. This could be hot air and smoke so allow time for the steel from the fire box to transfer heat to the cooking space.
if you’re BBQ Pit does not have multiple temp gauges you will need to get some temp gauges to put on the Pits cooking grades, oven thermostats will do fine. BBQ Tuning Plates are designed to be adjusted horizontally. Look at you’re temp gauges if one is hotter than the other. On the hotter side close the plates were there is less hot air coming threw and the colder side open the plates. Then close the Pit give it 15 min to recover and adjust again. You will adjust less and less as you get as you’re Pit gets closer and closer to even temp.