Running pre IAT is not a fail safe.

The only way to have a fail safe is to run separate fuel maps and wire in a hobbs switch so that as soon as pressure is lost in the line then it drops you down to the low octane table.

Either way, link is very involved. I highly recommend you activate the meth via link. It can be done other ways but not anywhere as easy to tune for as link won't know about the added fuel.