Ok. Ill just tell you guys whats the deal with this thing and maybe I'm barking up the wrong tree all together. Little back story... We did an engine swap. Its a 7.3 IDI non-turbo that came out of a school bus. I heard it run, and it sounded and ran great. Bought the motor, did the swap, leaving its injector pump on. The engine has a little trouble starting, but it fires up and idles fine. When your going down the road its fine, but lets say your coming up to a stop. You let your foot off the petal the truck stalls out. If you let your foot off the pedal slowly it wont stall, kind of keeping the rpms at 2,000. The mechanic I'm using right now is pointing to the injector pump.
My question now is: Is it the injector pump? Or could it be something else?