My persoanl review on this product is that it's pretty damn amazing. I was originally going to purchase a cheaper option, but I was really happy with my current exhaust sound (Motordyne Shockwave) and I didn't want to change it much. So after much deliberation, I decided on these FI resonated. Took about 5 weeks from order to delivery. Great customer service.
Here are some vids. For me, the most important factor was in-cabin noise, and so that's how these are recorded. There's not much to look at, there just from my phone, but they do the job.
Pre HFC early morning cold start
Pre HFC In cabin acceleration
Post HFC cold start
Post HFC In cabin acceleration
The HFCs pretty much double the sound of the exhaust when I'm really getting on it, but when I'm just cruising along, I can hardly tell a difference. There's no hiss on deacceleration, no drone in cabin and no ratteling. I did notice a slight whistle sound when first opening her up each time, though.
Also to note, my mechanic gushed over the quality of the part and the welds, going so far as to say, "These look so good it's ashame we have to put them under the car."
I got for a tune on the 11th, so look forward to one or two more videos. If anyone is interested in more or different views because they're considering these HFCs, let me know and I'll record something.