dumped,
Could somebody please take their big power 4 injector car upto 175mph odd the short one injector intermittantly as if its failing then turn it off and let me see the safe results?

SECS,
The SECS S8 ecu will NOT drive an injector unless it detects a resistance just before a pulse is sent to it.
So provided the intermittent problem is electrical then 99% of faults
like this can be safely detected.
A fault code will be registered and that whole faulty cylinder will be
shut down to prevent such a situation arising.