I made a video. Me trying to explain it isnt going so well ha ha. I can tell you where it drops off is right at the high point of second gear and it refuses to get enough 'get up and go' to run in third gear. Maybe 5-10 max mph before it drops off like that. Its also not exactly the same behavior when you give it gas. To get the truck going into that 5-10 range you really have to feather it to keep it from stumbling earlier than that.
https://youtu.be/_XV4xJVREMg