'93 S-10 4.3-tranny shifts hard then normal

Trans acts as though the vaccum hose is leaking or removed.(which has been checked) Trans shifts hard and appears it is in default mode as it will only shift at certain speeds. 18 mph 35 mph and 54 mph. At times it will go for days no problems. Just before the trans starts to act up the engine will cut off(very fast as if the ignition was turned on / off very fast) and the engine service light will come on. The computer will reset when ignition is turned off and when truck is started sometimes it may take 5 minutes to 3 days to go back to what seems a default setting. A friend at a car parts store suggested changing out the MAP SENSOR. This I did and for about 3 weeks all was normal. Then the same problem started again and slowly progressing to the stage why I changed it the first time. Any help from someone that hates these sensors as much as I do ? I intend to change over in the future and delete the entire system. Thank You in advance

Hoggie