I can't speak much on the multiple inlets, as I have a single inlet @ 2", and a single exhaust @ 2", however; if you could answer a few questions we may be able to help you a bit better. When you're at 225*, is that wide open on both inlets and exhaust? Rule of thumb is to leave the exhaust wide open at all times. Could you tell us about how you start your smoker?
The only other issue I can see is with your fire basket. Is it sitting directly on the bottom of your UDS, or is it elevated above where your inlets are positioned?
Give us some more info, and I'm sure we'll come up with an answer for ya! Pics of your set-up help as well!