have you tried this one:
15A** Fuel injectors (Shelby only)
or :
PCM vehicle power 4 – ignition coil Fuel pump relay? the issue with this one is that it cuts the fuel pump as well, this can lead to a long restart wait as fuel pressure is built back up. I would try to find the split to the fuel injectors alone and put the relay in there.
Engine kill switch - EcoModder