jeff at fast did an 4 mil agressive dune port for me, I had fmf fattys on it, my motor ran great. Jeff told me I needed better pipes to go with the portwork, shearers or simular pipes are what he recomended. I got R2s and can not beleive the dfference. the right pipe to go with your portwork is a huge gain. portwork and pipes equal 20+ hp easy