UPDATE
plugged in the standard ECU, turned the ignition to on... no ticking or any funny business, the fuel pump primes and everything seems normal. I just don't want to start the car with the bigger injectors / AFM.
Does this point to a cooked PowerFC? When I was first wiring up my AFM a while back the car would only run with the standard ECU, not with the PFC and it was fine (was a fuse issue), so I'm not going to write off the PFC just yet