I have a 91 R3500 with a gen v 454. I have a ALDL adapter and was watching my values when pulling my camper. When I put the truck in 4 gear and the lock up converter kicks in I notice that my timing goes retard and my Map sensor values go into the red and this is with over 50 percent throttle. If I let off of the throttle below 50 percent the Map sensor values go back up and the timing goes back advanced. If if keep the truck in 3 gear it never gets more then 40 percent throttle so it doesn’t go into retard in timing.