wont notice any difference with an axle back, other than noise.. the exhaust on the stags are quite restrictive. especially the dump pipe.
if you want stock looking. i'de be looking for a fujitsubo legalis R.
jethro, scotty, and a few others have them, and they are definitely pushing the power..
you wont notice any real performance change until you change the dump. recommend paying scotty for one..
with a full turbo back you may notice 2 psi extra.. but the stock ecu should sort it..