I see the following "Never been chipped". What does chipping do and what is the negative or positive for "chipping"? "EGR delete". I understand that the EGR delete is to bypass emissions controls. Other than the fact it's likely at minimum slightly illegal, what are the benefits for having this done? What does it cost to do this roughly? [For valuation purposes] "New heads and injectors". What's the approximate cost of doing this work? Would this be considered an engine rebuild or just a partial rebuild? If the heads and injectors were done, should this eliminate in most situations any need to rebuild the engine for 200,000 kms or more? I know little about engines and am trying to understand the basics.