Originally Posted by axmea?

594 here. Resonated HFC (last minute addition to the order) and Non-resonated CF. After having the car for 19 days, I could tell you that FI was the right choice for me. The performance gain is very noticeable. There is a very big difference between stock and the pcs Tony installed. It was loud the first week and toned down a bit after that. I would say that the cold start SPL was reduced by about 10% from when it was newly installed. I was a little self conscious and concerned about waking up the neighbors with the cold starts for the 1st week or so. To me, starting up the car was better that a nice cup of joe. You will be tempted to drive the car at higher rpms and shift at around 3.5 to 4.5 and occasionally higher (really mostly higher). This combo for me just sounds amazing. I'm inside and really want to hear how it sounds outside. I'd probably have an accident in my pants if I were. On my drive to and from work driving under bridges and through the two tunnels (one of them a short truck route tunnel on southbound 5 - which unfortunately is one of the unsafest tunnels around CA), I simply smile and lust over the sound this exhaust delivers.
I find it amazingly loud and am extremely satisfied with the order.