While performing an Offline installation of SP 2013 with SP1 on Server 2012 R2 it errored out stating that it couldn't download WCF Data Services 5.6 which I already had added to the prereq folder. I modified line 664 in AutoSPInstallerFunctions.ps1
/WCFDataServices56:`"$env:SPbits\PrerequisiteInstallerFiles\WcfDataServices56.exe`"
/WCFDataServices56:`"$env:SPbits\PrerequisiteInstallerFiles\WcfDataServices56.exe`"