Welcome neighbor, I'm down in Seattle. DPK had it right, everything from the cat back is fair game in terms of emissions. This is also not going to be a warranty problem unless you get into the cats, do that and you're taking on risk outside of any emissions concerns. Because you're asking in the first place you're probably aware of the downsides but I'll throw out a couple of obvious considerations. Emissions is one thing, many municipalities of sound ordinances, most don't enforce them in any systematic way but some do. If you park in a garage be prepared for the possibility that you will be setting off car alarms before you can get out of the garage. Do it for a while and you're going to be feeling some blow-back which can range anywhere from keying to violent confrontation. Ears ringing when you get out after a long drive... Yea, your hearing is taking a hit which will be permanent. Young people tend toward not caring while ironically making fun of old people saying "What, huh?". IMO it's money ahead to get an exhaust such as you see velocity preparing for sale. Push a button and you've got loud, push it again and back to quiet. Thats win.
