So then you have the older version of the Uego. I'm not positive if that one will work with the AEM utility. I didn't look that closely at the code when I decompiled it. If it doesn't say that it is getting connected in the utility then it might not work with your Uego. The dropdown list is just to pick what units you want the AFR displayed in. For instance 14.7 AFR Gasoline = 1 lambda. In RR what Uego plugin are you using?
Copy and paste some output from the hyperterminal here for me to see.