Dosing urea and not having DPF filter in place is a bad idea. The surface of SCR cat will get fouled and clogged very fast not to mention carbon buildup on NOX sensors. The complete EGR DPF SCR delete package is a must for that reason. I have some old diesels that do not have DPF EGR and SCR not even CAT installed coming to my shop all the time and if everything is OK with the engine, injectors, air induction etc there is almost no exhaust smell at all. They puff a little cloud of smoke every now and then when floored but smell is almost absent ...or I may be just used to it being a diesel tech.