I was browsing through few of the tuner's website, bluechip, apr, etc.
stage 2 requires few hardware parts fitted before it can be tuned.

just wondering, is there any specific brand or model of the parts required? or any generic stuff will work?

there seems to be so many CAI, exhaust, fuel pumps, etc.

my old Nissan had a tune, but it was custom dynoed tune, so it didn't matter what brand or model of the parts i had. it would just tune as efficient as possible. since these tunes are generic, not sure if it matters.