I am not sure what you mean by FASTLOAD, how do I verify this?
I tried F8 anyways and it did not work (did not delete the entry from the Linux iso list).
I was testing my usb key like this "sudo qemu-system-x86_64 -machine accel=kvm:tcg -m 512 -hda /dev/sdc"
Here is the content of my .mnu file (that has been deleted from my usb key but keeps showing on the Linux menu)

=========================
[[email protected]:6 16:04:02 Iso]$ cat CentOS7_AutoInstall.mnu
# CDLABEL must match ISO volume label (usually file name)
# NTFS is not supported! use FAT32 or ext2/3/4
# ISO must not have spaces in path or name

title Auto Install CentOS 7 from Kickstart\n Auto Install CentOS 7 from Kickstart

#ISO is full path to ISO (no spaces)
set ISO=$HOME$/CentOS-7-x86_64-Minimal-1611.iso

#LBL=CD VOLUME LABEL OF THE ISO use \\x20 instead of a space
set LBL=CentOS\\x207\\x20x86_64

map %ISO% (0xff) || echo -e $[0147]%ISO% IS NOT CONTIGUOUS! && map --mem %ISO% (0xff)
map --hook
root (0xff)
echo
echo -e $[1174]WARNING: THIS WILL NOT WORK ON NTFS DRIVES (use FAT32 or ext2/3/4).
echo
kernel /isolinux/vmlinuz root=live:CDLABEL=%LBL% iso-scan/filename='%ISO%' rd.live.image vga=791 inst.ks=nfs:it-deploy2.intelerad.com:/srv/exports/ks/wkstn_centos7-dev-ah.ks
initrd /isolinux/initrd.img
boot
==============================

The file was put under _ISO/Linux folder on the usb key, next to the CentOS-7-x86_64-Minimal-1611.iso it was refering to. Is that location allowed for .mnu file?