Yes, the modulator pressure check and adjustment is described in BBB and in Technical Manual. You need a gauge with banjo type connection for M8 screw if I remember correctly. You also may file down a piece of metal plate to make an adjustment tool - you will see.
Just take the values of pressure from BBB and convert them properly to whatever your gauge is showing. There are conversion mistakes in some posts on the forum.
Again - I have no idea if this eliminates your issue.
Quote from our Technical Manual:
"I finally got a call yesterday from the mechanic, and my car is done. Turns out that the transmission passing gear issue was, and many of the "clean up" and "sorting out" issues he discovered were matters of adjustments as I thought. In the initial case of the kickdown issue, 1st there were wiring problems, wires on the tranny were in the wrong place. 2nd, there was a broken wire on the harness at the relay. When those items were repaired, then the solenoid was able to work. Manually, they were able to get the kickdown to work; however the solenoid did not give enough travel in order to activate automatically. They tell me that the final resolution was linkage adjustment AND a bent "rod". When they straightened the bend rod (I think this is that the solenoid pushes on in the tranny) and adjusted the linkage, voila, it all works."
This bent rod was the rod through which the solenoid pushes on madulator lever. Its length can also be adjusted.