There was a grey and while little long hair named Noah at the shelter i volunteered at last summer. Whenever he was given attention he would start by mewing softly, leading into a rumbling rocket purr accompanied by profuse drooling. I loved Noah, and luckily he was adopted. Probably a good thing- I don't think I could deal with all that drooling! It never stopped! Nito drools occasionally too, when we are doing tricks together. I think it's a combination of purring, and desiring his favorite tasty treats that makes his mouth water.