Does anyone do this? It seems like an interesting business to get into and would alleviate a lot of the anxiety people have about modifying (illegally) their emmissions controls. For example, I bet a much better EGR system could be designed and EPA certified that would allow high HP applications without the problems the stock one gives. Since the stock one was made for the stock flow and power levels, it is not a surprise that it chokes (literally) when we mod these trucks.
Same goes for the newer DPF system. Just like you can get high-flow cats, why couldn't a high-flow DPF be developed? I think there are plenty of people who would buy these items to remain compliant, yet get to play.