No muffler will give you the horsepower you want. Only real engine mods along with exhaust mods will give big horsepower. Do a full open intake with a completely custom exhaust and throw in headers while you are at it...this will give good power increases.
warmonger
Former owner of '99 CSVT - Silver #222/2760
356/334 wHP/TQ at 10psi on pump gas!
See My Mods
'05 Volvo S40 Turbo 5 AWD with 6spd, Passion Red
'06 Mazda5 Touring, 5spd,MTX, Black