MDW: Welcome to the TDR, the best source for helpful answers on the many questions that arise when you are new to turbo-diesels. I agree with beginning by repairing the start-and-stumble and exhaust system problems. Next I would suggest guages, EGT(Exhaust Gas Temperature) and Boost. This will give you a means of monitoring the effect of any subsequent modifications and avoiding potential problems. Before any power mods, I would also suggest that you increase the intake air volume by changing to a K&N in the stock air box, a Scotty or a Psychotty. Use the search function in this forum to find all kinds of helpful material on these and other modifications. Good luck and Happy Bombing!
Cheers, Pete.
------------------
'97 2500 CC 4x4 5spd 3. 54LSD all stock except K&N Air, EGT&Boost Guages - next Psychotty & 4" exhaust