Valve ticking ???

Good day folks, Got back this morning from 4 wheelin in North Dakota. My tow rig has devloped a ticking noise similar to valve tick in gas engines. 300 miles down all seemed OK other than mileage. 300 miles home. If I recall correctly my OEM pump gave me 19 mpg (Canadian gallon) unloaded & 14 mpg loaded. Now with new Stad injectors & a DPS pump I'm @ 21 unloaded but only 10 loaded. Now truck has this noise. Swung by diesel shop & they said these engine are known to pound the valves into the head. Is this true? By the way I now have a heating issue under load. Pulling in Montana flat grade @ 800 EGT. Slightest increase will give me 1000. Can run there for a very short time before engine temp begins to rise. Mech temp sensor in drivers head would goto 230 then I would back off the fuel. Running in direct @ 62mph & 2500rpm. Did I cause some problems with the heat? The factory guage only ever got to the "A" in normal before I got off the pedal. THX much.