I found a 1998 dodge 2500 12 valve diesel with 115000 miles and it seems doggy compared to our 94 with 290000 miles. I did not notice any strange noises or see any visible problems with it, what gives?

 

Could be a dirty fuel filter or air filter, its amazing how bad an engine will run with dirty filters. We dynoed a jd 4430 tractor at work one time that the guy said had no power, he didnt do any maintanence and never changed the air filter, when we pulled the filter out it was just caked with dirt, put on a new filter and the tractor dynoed 30 more hp.
Thats a good place to start anyway, a stock 98 motor has a few more hp than a stock 94 does so it should actually have more power, are they both the same trannys?, sometimes if you drive an auto then jump in a manual truck it might seem more doggy, other than that I'm not real sure what it could be. Good luck

 

they both have the same 4 speed with over drive tranny. I'll check the fuel, oil and air filters.

 

I know when I got my truck the fuel filter and plugged I changed it and put a K&N filter and swiss cheesed the air box made a big difference. OH and cut the muffler and cat off thats supposidly is goin to gain you 12% more power. thats a Diesel Power Mag said on the poject 12v