To be honest, I had the FI 18" resonated catback and I absolutely LOVED IT!! I went back to the stock exhaust and it's very.. lackluster for a lack of a better word. I definitely miss the FI exhaust that's for sure.
By the way, there was nothing wrong with the FI exhaust. I loved it. I switched back to OEM because I'm awaiting a new exhaust to come in. Hint. Quad tips.
If you're deciding on what exhaust to get, look no further than the FI 18".