Considering a removal of your Cummins ISX engine's pollution control system? A “delete,” generally referring to the bypassing of Diesel Particulate Filters (DPFs) and Selective Catalytic Reduction (SCR) https://medium.com/@shine.santhosh61/improving-heavy-duty-diesel-engine-performance-through-smart-calibration-and-maintenance-26a2a6b1d26d