Just fitted a Firestorm and decat centre, what should me my next mod to increase power on 2002 wagon(WRX)?
With the above in mind will the PPP be cheaper as i would not require the exhaust mods?

If you bargain hard at a Subaru dealership, you may get:

"Well sir the ppp is a package, and I'd have to contact IM to sanction this request, though that would involve us completing a thesis of no less than 1 million words......yawn, red tape blah blah"

Though I'm sure you'll come to some satisfactory result, good luck