voltage is not right
 

I have a S4 tii , my car has a lot of problems, and I try to fix it .
my car is running lean and stumbling(18.0-19.0)under light throttle
I test my ecu today , and found out 3E (front primany injector)3F (rear sec)3H (front sec) has lower voltage than the spec , it show 8~9v on my meter .
but 3c (rear primary) is normal ,12V , why would this happened?
I have new 720cc secondary injectors , and new injector plugs.
also AFM is under 1v , I have 3 spare AFM , they both showed under 1v

Is this a car with the solenoid resistor and low resistance injectors..........or one that came with the high resistance injectors?

If it has the solenoid resistor I'd take the plug off it and ohm out the circuit for each injector from there to the small ECU plug (disconnected from the ECU) and compare the resistance of each injector circuit to the other.

The AFM? Got me. I'd go to the afm connector and pull it off. Then take a look at the incoming voltage of the Brown/White wire. It should be 4.5 to 5.5 vdc.

Did you check the injector voltage with the car running or just with the key to ON?

Your reading the ECU plugs from the wire side of the plug counting from the right and working your way to the left in a up/down fashion?