Dyno gains +14whp / 22ft-lbs – The Supreme SP for the Subaru STI Sedan features much larger diameter piping, resonators and mufflers, but also smoothes the layout for maximum performance with good sound suppression. This cat-back exhaust starts out with a full 3” mid-pipe with a large straight-through resonator to tune out drone. The next section smoothly transitions into dual 2.5” diameter piping. Improved dual GReddy straight-through mufflers with dual, double wall tips on each muffler finish off the exhaust. GReddy designers carefully position the dual mufflers and staged tips to flow with the GV-chassis’ bodylines. Like all GReddy Supreme SP systems the fully hand-welded 304 Stainless-Steel exhaust carries a Limited Lifetime Warranty.