MAF conversion

[Jerry77]

I have an '88 5.0 speed density, bone stock that runs "perfect" with the DA1 computer.
I aquired a second '88 SD computer harness that I added the 4 wire MAF conversion harness, an A9L and a 19# Ford MAF meter. I drove the '88 home and draped the new harness over the fender and had the engine running with the mass air within the hour. I has a "hunting" idle and I only idled it for about a minute; since I felt this wasn't right. I substituted another Ford 19# MAF meter and it made no difference. I checked the MAF harness at idle and there was the 5vref and a 1.76v return voltage.
I think the MAF meters are bad or the computer is bad. How should I verify this? With this simple conversion I thing the engine should have idled perfectly from the start.
PS: This harness and A9L will be used on my project car, a 390FE with EEC-IV. This harness idled on the 390FE; but wasn't idleing perfect and had a stumble when you open throttle from idle.
This is why I tested harness on the '88, to see if harness and computer were okay.
All the '88 sensors are ok, since I just drove it home. How does a bad computer act?
Thanks for any help.