Re: the "sucking sensation"... I think I was in the right area but on the wrong track. I improved on it a bit by playing with the A/T throttle cable tension. It was tough to tell with my tach needle burnt out, but it appears to actually be an awkward up/down shift just under 2,000 RPM and 55-60 mph. It gives the sensation of being pulled backward by your shoulders, which is what I attributed to the throttle plate being sucked closed.
I couldn't make sense of the various explanations of how to properly adjust the tension, so I'm pretty much taking shots in the dark until it feels right...
'94 SC400: Goodkat ... "It's not something people hear about. Falls on deaf ears mostly. This particular one has been over twenty years in the making."