Any HP gains with the HONDA sport muffler for my Si?
Yup. Good thing I moved to RI from MA.Honda is careful to not say it changes the sound. They only mention sporty "appearance".
It does however produce a slightly deeper sound and it looks sort of like an aftermarket exhaust-enough to have been already stopped by a 'Statey" who was having a bad night. (F'n Mass says ANY modification to produce more sound is illegal)
If you're in the market, make sure you shop around as prices vary wildly.
It will get a little louder after 2-3 weeks of driving also. After everything breaks in it gets a nice deep louder tone to it. No HP gains but w.e.Okay so the sound is a bit better now that I drove around more and got the exhaust heated up. Here is a video of it:
YouTube - 2009 Honda Civic Si - HFP Axle-Back with Intake Resonator Delete