I went from having only an aftermarket 3inch cat back exhaust and then bolted on one of BATMBL's combo pipes. I don't have dyno results with the current setup but I can tell you there is definately a noticeable power increase from the mid range to the top end of revs Standard CAT still in place too, for now!
A slightly more aggressive exhaust note - which can be heard from the drivers seat AND standing outside at the back of the car!
I wouldnt even call my current setup "standard boost" as the needle goes so much higher than a stock setup [inc. airbox and exhaust]. When I increase the boost it makes possibly more of a difference than before - due to the increased pipe diameter / air flow...
Dunno if this helps much though? But I am very happy with my exhaust atm, do the cat and then i will be finished. For info cat-back section is Fujitsubo piping / resonator with a Kakimoto full body muffler = nice note, NOT loaud
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