If you are looking for mileage you are going in the wrong direction,The RPM intake is just what it says,RPM! larger runners for increased fuel delivery,to get mileage you want an intake with smaller runners to produce increased low end torque and promote higher velocity at lower speeds,the cams discussed above will not promote fuel economy either.I am not really sold on the regular Performer intake either,you'll find tons of them on ebay and craigslist for $50.So lets look at this combo to get you going in the right direction,plug in these part#'s at www.summitracing.com Weiand 8125,Crower CRO-00904,Summit SUM-M08600VS .Hopefully Techinspector can run some numbers for you.