I'm looking at buying this 03 Duramax 2003 2500HD 4X4 crew cab auto. LOADED 153,000 I know it's the early generation engine, I forget which engine is in the 2003. but... I've heard horror stores about the engines.. and I've heard some guys have never had an issue at all. Question: If I was to buy this ? And I started to notice problems with the performance. What can I do to this engine to make as good as ... maybe the LLY ???