Electrical MAF sensor readings

Hey guys I have an odd issue. Have a 302 out of a 91 mustang in a jeep YJ. We used a new Painless harness and a used A9L ECU. The issue I was having was it seems very Rich and doesn't like to idle. I pulled the codes and all it has is codes for the egr and canister purge which this swap has neither.
I checked voltage on the IAT, ECT, and TPS all look good. When I check the MAF it has the correct 12v and ground. The issue I find is the with the key on I have no ground at the signal return wire. It reads the same as the signal wire which reads battery voltage even when running. I assume this is why it is wanting to run rich. I've checked readings both at the sensor and at the ECU and they read the same. Is there a chance there is an issue in the ECU

I forgot to add it is a new BBK MAF calibrated for 24lb injectors and has new ford performance 24lb injectors

Yes correct I was not looking for a ground on the signal wire. I was looking for ground on the signal return/ecu sensor ground pin #9 in the ECU or pin C on the maf. I assume it is reading the same as the signal because the signal is looking for ground in the ECU?

The signal wire pin 50 ECU reads supply voltage 11.9v key on reads 13v running doesn't move with RPM. When I ohm between the signal and signal return I get 129k ohms. Everything I read says the signal return/sensor ground should show ground. And mine doesn't. Also yes the voltage readings you referenced above is what I was expecting to see on the signal but I'm seeing battery voltage. Just lost looking for the next thing to check.