How to uninstall rEFInd (0.8.2) on Yosemite
The gptsync_x64.efi program file was probably installed with rEFInd, but is a separate program. Leaving it in place should do no harm, but will also probably do no good, so it's a judgment call on your part. If you remove rEFInd, chances are the only thing that would run gptsync_x64.efi would be a subsequent install of rEFInd (or of its predecessor, rEFIt) or launching it manually from an EFI shell.