Have you thought about doing some porting work on your own? If you ask on here, info on what to do for starters to get about 50 to 75 percent of possible flow gains can be done by the average guy taking his time. You could start by working with the valves you have, or upgrading the intakes to 2.14 size. Just doing the intakes will keep the cost down, and I am betting on good gains, even leaving the exhausts stock. Some of the other posters here can maybe chime in on that last suggestion.