90 power ram

ok had this truck for about 2 weeks and the injection pump was just replaced 20k ago and has a air dog 150 i think on it i dropped it off to have universals on it and i think the guy ran the tar out of it because i dropped it off with 3/4 tanks of fuel and it came back with 1/4 tank and the over heat code was on it to along with 2 different code for a map sensor. can you tell me what this guy did to my truck he had to have beat the hell out if it. i drive it hard some times but im really easy on it and it seamed low on power to. new to the 24v had a first gen 12v for about a yea so still new to the Cummins diesel

thanks shane