bone stock except for tune. 2008 evo x MR. v403 AP. will adding a hff change much? cobb's own site is very vague on details between stock stg 1 map and stg 1 hff map.

 

I had alot of issues and went back to the stage 1 with stock filter. High knock counts and overboosting. Check out my thread for more details. I would get an exhaust before screwing with the intake

But to answer your question, yes it is a huge difference. Turbo and b/o valve are alot louder and def more power.