The drawback on not having a urea tank is requiring the several times the EGR flow to meet emission requirements. And FWIW the new cummins engines DO NOT meet them, cummins is burning epa credits it earned from 07 model year+ that exceeded the 07 requirements.
2007 Chevrolet 3500 CC/LB Duramax/Dually 4X4 Mine r4tech, Reese Signature Series 18k +slider, duratrac, Titan 62 gallon, diamond eye, Cheetah 64
2011 Keystone Fusion 405 TrailAir & Triglide, Centerpoint, gen-turi, 3 PVX-840T, XANTREX FREEDOM SW3012, G614