I recently had an engine swapped from a 1995 truck into a rust free truck that had a a blown engine. The engine is running strong, however when I accelerate the truck seems more sluggish than before. The truck is also surging when I need to apply power quickly and up hill. It jumps from 2400rpms to 3000 rather abruptly. When I run the truck in OD I don’t have this issue. If anyone has any insight to what my problem could be I would greatly appreciate the help.