While I can't comment on the LB7 coding with a blocked EGR. I can tell you from experience that Cali and Northeast LLYs will code and limp with EGR blockage. I always thought LLYs and LBZs would all limp with an EGR block and no tuning based on some experience dealing with trucks locally. When people started telling me otherwise, I knew my experiences couldn't all be flukes, then I found a nice write up breaking it all down on Kennedy's siteIf its a 01-04 LB7 (or at least thats where you've posted) then you won't have either. Some California Emissions LB7s had EGR but should be like the LLY's, no tuner needed to delete or block off).
Only 07.5+ (New Body Style Trucks) had a DPF present. GM never put anything other that a Catalytic Converter in the exhaust stream (other than EGR) on 01-07 Classix Body Style Trucks.