I think you want to have the least restrictive air flow in and exhaust out. Some of Bank's ideas for power enhancements allegedly will also give better fuel economy. There are other aftermarket stuff (as you know) that will sorta duplicate Bank's stuff. Also, does your programmer have the option of downloading an "economy" file? Any "restrictor plate" will probably reduce horsepower and reduce efficiency.
ATS Arc Flow Intakes for Cummins - ATSArcFlowforCummins