IMO you don't gain much with a intake, get a good high flow air filter, I have a Perrin in the stock box. I'm catless up/dp in my 05, with stock exhaust, sounds pretty good, if you want more noise from the stock exhaust check out this.
Even with the exhaust the hp gain is about 10-12, is it worth the money.
You can do the washer thing now and see how you like the sound. Or do what I did, I removed the mufflers from my 09 Spec B and put the muffler deletes I had made for the wagon years ago, on it.
193k, 5/20/12 new ej257 short block, 8/20/11 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. CHECK your oil, these cars use it.
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