TCC and I took Angel to the vet's today to have her ears checked for ear mites or an ear infection, which you can read about here:
http://www.yorkietalk.com/forums/showthread.php?t=45156. We asked about her gagging, and the vet said it's nothing to worry about if she doesn't do it often. She said that she doesn't think it's acid reflux and that she could be clearing her throat of something.