imho and through experience i can say i fitted the SPT induction kit (item SOA8431000 from http://www.subaru.com/subaru-perform...ce-parts.html#) and heatshield as most other performance cars i have had the first steps are normally to sort out engine breathing, eg exhaust and intake. Fitted the SPT kit along with prodrive exhaust etc and had Duncan (RaceDynamix) remap it for me. Worked a treat no snags and intake temps were acceptable.

Went to the next step and fitted VF35 etc etc and had Duncan remap it again and suffered really bad surge under load, Duncan said the induction kit was flowing too much air and had to trim the boost curve right back to make it safe, gutted.

Took his advice and bought a simota panel filter and was going to refit the stock airbox, booked into Rowleys to do all the mapping work post airbox fit. Decided whilst there to do a dyno run with the SPT fitted so i could get before and after figures and low and behold Duncan worked his magic again and optimised the map with the SPT induction kit resulting in no surge and 338.9hp. He advised me not to bother re-fitting the standard airbox.