1995 Toyota Previa 95 Previa SC hesitatation

Have a 95 previa w/ 165,000 miles just a baby for previas. Had the transmission and radiator flushed. Now the tranny slips at low rpms. Previous to that it had an occasional miss (engine).I went back to the repair shop to see if they filled the tranny properly. They said it's an engine issue not the tranny.I took it to the dealership and they say its the SC. It has parameters programmed into the computer that cause the SC to 'choke' when the engine has wear and 'wobbles'. Is there anyone out there who has had this issue. Short of having the engine overhauled is there any way around the SC specs? Can the computer be reprogrammed to a wider range? Or could this be something that the technician is missing. Like the tranny could now have something going on from the flush.I didn't have the tranny serviced. Just flushed. Or could this be some other issue w/the SC that might be fixable? I have owned 2 other previas (no SC) so this is a new issue that seems to be more of a transmission slip than a SC problem. And it seems strange that the miss in the engine just suddenly started to effect the transmission performance? The other strange thing is that it is intermittent?