It doesnt sound like the ecu is damaged as fried inj drives usually stay on all the time - so you know pretty quickly when the engine fills up with fuel.
So possibly a fried wire somewhere.
I would start by unplugging the B connector off the ecu and put a multimeter or test light straight onto the inj 5 or 6 pin. You will have to temporarily set the number of cylinders to 4 so that inj 5 & 6 are considered aux outputs and will give you the test setting. So if it is set to off you should see +12V on the pin and if set to "Test (ON)" it should be near 0V. This will at least confirm if the problem is inside the ecu or something else.
