p0447 what is it?

I have had a recurring code recently (p0447), used to come on every so often and now that inspection is due it is being persistent. I had a large leak and some other evap codes months ago and replaced gascap and hoses and everything went away. I have always had to fill fuel slowly or pump would shut off and have seen other posts with same issues and no answers. I was hoping someone has some info. it would be appreciated.