First of all, kudos to you for recognizing it! My 4 yr old had that too, but we just thought it was cute that he snored so we didn't take him in right away. We did end up at the pedi ENT when he couldn't hear because of so much fluid on the ears (also caused by huge adenoids blocking the eustachian tube). The doctor asked me to show him a video of my son sleeping so I took a five minute video on my Flip camera. You could see/ hear the sleep problems and constant changing positions to get air. The doctor also pointed out how his chest was pulling in...trying to drag in air instead of expanding out with oxygen. Said his heart was having to work so hard. He said this was actually a serious issue...that ENTs are taking more seriously now because it can cause heart arrythmias, enlarged hearts, stunted growth (from sleeping in a low O2 environment), and slows mental development with reduced REM phase sleep time.
Needless to say, we had his tonsils and adenoids out a few weeks later and all is great now! He's eating a ton now, so I'm hoping he'll go through a catch up growth spurt. Btw, I now have met three other moms who had the same issues with their sons...surgery fixed them all.
Good luck. Surgery isn't fun and recovery can feel long when you are cooped up. Make it like Christmas with gifts for sedentary play. I even brought some small things to the hospital and told him he would get them as soon as he woke up. He didn't forget and it seemed to shift his focus. Good luck! Lots of prayers!