The Duramax LB7 fuel injectors are common problem. Due to the extreme pressures of the direct injection, which is what the LB7 diesel engine has, along with a good amount of carbon build up common to di systems, these injectors fail. The injectors are not easy to reach, and there are many low cost (garbage) injectors available to be careful selecting replacements. You don't want to replace the injectors again anytime soon. If you're experiencing hard starts and poor fuel economy bring your Chevy diesel truck to Garrett Auto and Truck Service for diagnostic and repair service from expert diesel engine mechanics.