OK folks. I wanted to circle back around on this and maybe save you all some headaches.
If you need a vacuum modulator for your A4LD, think twice about using the Pioneer part #747008 I linked above. It is listed as correct for both the Ranger and B4000 on multiple sites including O'Reilly and Rock Auto and on Pioneer's own site. But it's either not right for my 94 or I got two faulty ones out of the box or maybe both.
I finally gave up trying to solve this myself and brought it over to my local trans shop and told them what I had done so far. They know the A4LD well and I'm sure it has put meals on their plate for many years! They took a look at the modulator and said it didn't look right to them compared to what they use. Even though it fit just fine and looked similar to the old one I had in there before they were not convinced it was right. They ordered a different modulator from their supplier (I'll try to find out brand/model), installed it and now the trans shifts fine. No problems with the governor or anything else. This makes me both happy and annoyed at the same time.
