A BHAF would help. Do you have a stock airbox? A cold air intake of some kind would probably help. I have an AFE stage 2, though there are several different brands. I also assume your 4" exhaust is all straight piping, no cat or anything? You shouldn't need a bigger turbo with your mods, i have a 40 and it cools quit well for me, though I only have 60 HP injectors.