It will work on EFI. I am still thinking there's a fault somewhere else. Have you had any luck trying to pull error codes from the ECU since you've swapped parts? Is the distributor set correctly? I've run into situations where the distributor has been out by '180 degrees' and it's pretty common (it's not exactly 180 degrees due to the odd number of gear teeth) If the O2 sensor wasn't working you'd get an error code from it.