The injectors are grounded through the ECU. When the key is on, you would expect each injector to have constant +12V on one pin and open circuit on the other.
On these cars, all four injectors fire together and are wired in parallel.
The grounds are found on the two bolts that hold the fuel rail to the manifold.
What do you mean about the noid light flashing when the key is off? Are you engaging the starter directly off the battery or is the engine stopped when it flashes?
The injectors shouldn't have power at all when the key is off, I think if the manifold grounds are good and the ground between the block and chassis is good, maybe look at the white fuel pump relay next, and check for 12V to the injectors with the key on.
