I was thinking bout getting a header for my 02 WRX. So far I have a SR30, DR500 FMIC, STi Injectors, MRT UP/DP, B&B Cat Back, ECUtek, and some other stuff. I was wondering how much power I could pick up off of a header. Would I see quicker spool? My friend said he got better gas mileage with his HKS header. What header would you pick?