I have a 91 f150 with a 5.0 that I did a MAF Conversion with a mustang A9L PCM. The DYNO guy wasn't happy with me only having one O2 sensor. So per his instruction I have a Ford O2 sensor from Ford (80 effin dollar sensor) for my year truck and am a little hesitant to go off mix matched diagrams I've found online.
Any input, instruction, or info would be greatly appreciated.
P. S. All the info on what's done to the truck is on the forum "SD to MAF Conversion". I'll try to put a link in.

 

SD to MAF Conversion
(Small Block V8 (221, 260, 289, 5.0/302, 5.8/351W))
32 03-15-2016 by RIKIL

 

https://www.ford-trucks.com/forums/1418130-sd-to-maf-conversion.html?highlight=MAF+Conversion

 

Why? Does the truck have dual exhaust? You did a DIY MAF conversion so what did you do with the single O2 sensor? Did you tie it to both A9L sensor inputs? That works just fine and is exactly what Ford did with the MAF conversion kits they produced for these trucks, but if you gotta have dual sensors then just install a second one in the drivers side header and wire it to the PCM, the input pins for the O2s are listed in the other thread you linked above.

 

Don't mean to hijack here...but I due to clearance issue I'll be running single O2 with mustang ECU. When you say tie into both sensor inputs, you mean splice a 2nd wire from just the output wire to the other input pin? Just connecting the output from 43 to 29 from the sensor? Nothing to do with the ground right?

 

That is right you just need a little jumper across those 2 pins or the wires leading from those pins anywhere along their length, that is it.